// ========================================================================== // Project: SproutCore Costello - Property Observing Library // Copyright: ©2006-2011 Strobe Inc. and contributors. // Portions ©2008-2011 Apple Inc. All rights reserved. // License: Licensed under MIT license (see license.js) // ==========================================================================

sc_require('ext/function'); sc_require('private/observer_set'); sc_require('private/chain_observer');

//@if(debug) /**

Set to YES to have all observing activity logged to the console.

This is only available in debug mode.

@type Boolean

*/ SC.LOG_OBSERVERS = false; //@endif

SC.OBSERVES_HANDLER_ADD = 0; SC.OBSERVES_HANDLER_REMOVE = 1;

/**

@class

Key-Value-Observing (KVO) simply allows one object to observe changes to a
property on another object. It is one of the fundamental ways that models,
controllers and views communicate with each other in a SproutCore
application.  Any object that has this module applied to it can be used in
KVO-operations.

This module is applied automatically to all objects that inherit from
SC.Object, which includes most objects bundled with the SproutCore
framework.  You will not generally apply this module to classes yourself,
but you will use the features provided by this module frequently, so it is
important to understand how to use it.

Enabling Key Value Observing
---

With KVO, you can write functions that will be called automatically whenever
a property on a particular object changes.  You can use this feature to
reduce the amount of "glue code" that you often write to tie the various
parts of your application together.

To use KVO, just use the KVO-aware methods get() and set() to access
properties instead of accessing properties directly.  Instead of writing:

      var aName = contact.firstName;
      contact.firstName = 'Charles';

use:

      var aName = contact.get('firstName');
      contact.set('firstName', 'Charles');

get() and set() work just like the normal "dot operators" provided by
JavaScript but they provide you with much more power, including not only
observing but computed properties as well.

Observing Property Changes
---

You typically observe property changes simply by adding the observes()
call to the end of your method declarations in classes that you write.  For
example:

      SC.Object.create({
        valueObserver: function () {
          // Executes whenever the "Value" property changes
        }.observes('value')
      });

Although this is the most common way to add an observer, this capability is
actually built into the SC.Object class on top of two methods defined in
this mixin called addObserver() and removeObserver().  You can use these two
methods to add and remove observers yourself if you need to do so at run
time.

To add an observer for a property, just call:

      object.addObserver('propertyKey', targetObject, targetAction);

This will call the 'targetAction' method on the targetObject to be called
whenever the value of the propertyKey changes.

Observer Parameters
---

An observer function typically does not need to accept any parameters,
however you can accept certain arguments when writing generic observers.
An observer function can have the following arguments:

      propertyObserver(target, key, value, revision);

- *target* - This is the object whose value changed.  Usually this.
- *key* - The key of the value that changed
- *value* - this property is no longer used.  It will always be null
- *revision* - this is the revision of the target object

Implementing Manual Change Notifications
---

Sometimes you may want to control the rate at which notifications for
a property are delivered, for example by checking first to make sure
that the value has changed.

To do this, you need to implement a computed property for the property
you want to change and override automaticallyNotifiesObserversFor().

The example below will only notify if the "balance" property value actually
changes:

      automaticallyNotifiesObserversFor: function (key) {
        return (key === 'balance') ? NO : sc_super();
      },

      balance: function (key, value) {
        var balance = this._balance;
        if ((value !== undefined) && (balance !== value)) {
          this.propertyWillChange(key);
          balance = this._balance = value;
          this.propertyDidChange(key);
        }
        return balance;
      }

Implementation Details
---

Internally, SproutCore keeps track of observable information by adding a
number of properties to the object adopting the observable.  All of these
properties begin with "_kvo_" to separate them from the rest of your object.

@since SproutCore 1.0

*/ SC.Observable = /** @scope SC.Observable.prototype */ {

//@if(debug)
/* BEGIN DEBUG ONLY PROPERTIES AND METHODS */

/**
  Allows you to inspect a property for changes. Whenever the named property
  changes, a log will be printed to the console. This (along with removeProbe)
  are convenience methods meant for debugging purposes.

  @param {String} key The name of the property you want probed for changes
*/
addProbe: function (key) { this.addObserver(key, SC.logChange); },

/**
  Stops a running probe from observing changes to the observer.

  @param {String} key The name of the property you want probed for changes
*/
removeProbe: function (key) { this.removeObserver(key, SC.logChange); },

/**
  Logs the named properties to the console.

  @param {String...} propertyNames one or more property names
*/
logProperty: function () {
  var props = SC.$A(arguments),
      prop, propsLen, idx;
  for (idx = 0, propsLen = props.length; idx < propsLen; idx++) {
    prop = props[idx];
    console.log('%@:%@: '.fmt(SC.guidFor(this), prop), this.get(prop));
  }
},

/* END DEBUG ONLY PROPERTIES AND METHODS */
//@endif

/** @private Property cache. */
_kvo_cache: null,

/** @private Whether properties of the object will be cacheable. Becomes true if any one computed property is .cacheable() */
_kvo_cacheable: false,

/** @private Cache of dependepents for a property. */
_kvo_cachedep: null,

/** @private */
_kvo_changeLevel: 0,

/** @private */
_kvo_changes: null,

/** @private */
_kvo_cloned: null,

/** @private */
_kvo_revision: 0,

/** @private */
_observableInited: false,

/**
  Walk like that ol' duck

  @type Boolean
*/
isObservable: YES,

/**
  Determines whether observers should be automatically notified of changes
  to a key.

  If you are manually implementing change notifications for a property, you
  can override this method to return NO for properties you do not want the
  observing system to automatically notify for.

  The default implementation always returns YES.

  @param {String} key the key that is changing
  @returns {Boolean} YES if automatic notification should occur.
*/
automaticallyNotifiesObserversFor: function (key) {
  return YES;
},

// ..........................................
// PROPERTIES
//
// Use these methods to get/set properties.  This will handle observing
// notifications as well as allowing you to define functions that can be
// used as properties.

/**
  Retrieves the value of key from the object.

  This method is generally very similar to using object[key] or object.key,
  however it supports both computed properties and the unknownProperty
  handler.

  Computed Properties
  ---

  Computed properties are methods defined with the property() modifier
  declared at the end, such as:

        fullName: function () {
          return this.getEach('firstName', 'lastName').compact().join(' ');
        }.property('firstName', 'lastName')

  When you call get() on a computed property, the property function will be
  called and the return value will be returned instead of the function
  itself.

  Unknown Properties
  ---

  Likewise, if you try to call get() on a property whose values is
  undefined, the unknownProperty() method will be called on the object.
  If this method returns any value other than undefined, it will be returned
  instead.  This allows you to implement "virtual" properties that are
  not defined upfront.

  @param {String} key the property to retrieve
  @returns {Object} the property value or undefined.

*/
get: function (key) {
  var ret = this[key], cache;
  if (ret === undefined) {
    return this.unknownProperty(key);
  } else if (ret && ret.isProperty) {
    if (ret.isCacheable) {
      cache = this._kvo_cache;
      if (!cache) cache = this._kvo_cache = {};

      return (cache[ret.cacheKey] !== undefined) ? cache[ret.cacheKey] : (cache[ret.cacheKey] = ret.call(this, key));
    } else return ret.call(this, key);
  } else return ret;
},

/**
  Sets the key equal to value.

  This method is generally very similar to calling object[key] = value or
  object.key = value, except that it provides support for computed
  properties, the unknownProperty() method and property observers.

  Computed Properties
  ---

  If you try to set a value on a key that has a computed property handler
  defined (see the get() method for an example), then set() will call
  that method, passing both the value and key instead of simply changing
  the value itself.  This is useful for those times when you need to
  implement a property that is composed of one or more member
  properties.

  Unknown Properties
  ---

  If you try to set a value on a key that is undefined in the target
  object, then the unknownProperty() handler will be called instead.  This
  gives you an opportunity to implement complex "virtual" properties that
  are not predefined on the object.  If unknownProperty() returns
  undefined, then set() will simply set the value on the object.

  Property Observers
  ---

  In addition to changing the property, set() will also register a
  property change with the object.  Unless you have placed this call
  inside of a beginPropertyChanges() and endPropertyChanges(), any "local"
  observers (i.e. observer methods declared on the same object), will be
  called immediately.  Any "remote" observers (i.e. observer methods
  declared on another object) will be placed in a queue and called at a
  later time in a coalesced manner.

  Chaining
  ---

  In addition to property changes, set() returns the value of the object
  itself so you can do chaining like this:

        record.set('firstName', 'Charles').set('lastName', 'Jolley');

  @param {String|Hash} key the property to set
  @param {Object} value the value to set or null.
  @returns {SC.Observable}
*/
set: function (key, value) {
  var func   = this[key],
      notify = this.automaticallyNotifiesObserversFor(key),
      ret    = value,
      cachedep, cache, idx, dfunc;

  if (value === undefined && SC.typeOf(key) === SC.T_HASH) {
    var hash = key;

    for (var hashKey in hash) {
      if (!hash.hasOwnProperty(hashKey)) continue;
      this.set(hashKey, hash[hashKey]);
    }

    return this;
  }

  // if there are any dependent keys and they use caching, then clear the
  // cache.  (If we're notifying, then propertyDidChange will do this for
  // us.)
  if (!notify && this._kvo_cacheable && (cache = this._kvo_cache)) {
    // lookup the cached dependents for this key.  if undefined, compute.
    // note that if cachdep is set to null is means we figure out it has no
    // cached dependencies already.  this is different from undefined.
    cachedep = this._kvo_cachedep;
    if (!cachedep || (cachedep = cachedep[key]) === undefined) {
      cachedep = this._kvo_computeCachedDependentsFor(key);
    }

    if (cachedep) {
      idx = cachedep.length;
      while (--idx >= 0) {
        dfunc = cachedep[idx];
        cache[dfunc.cacheKey] = cache[dfunc.lastSetValueKey] = undefined;
      }
    }
  }

  // set the value.
  if (func && func.isProperty) {
    cache = this._kvo_cache;
    if (func.isVolatile || !cache || (cache[func.lastSetValueKey] !== value)) {
      if (!cache) cache = this._kvo_cache = {};

      cache[func.lastSetValueKey] = value;
      if (notify) this.propertyWillChange(key);
      ret = func.call(this, key, value);

      // update cached value
      if (func.isCacheable) cache[func.cacheKey] = ret;
      if (notify) this.propertyDidChange(key, ret, YES);
    }

  } else if (func === undefined) {
    if (notify) this.propertyWillChange(key);
    this.unknownProperty(key, value);
    if (notify) this.propertyDidChange(key, ret);

  } else {
    if (this[key] !== value) {
      if (notify) this.propertyWillChange(key);
      ret = this[key] = value;
      if (notify) this.propertyDidChange(key, ret);
    }
  }

  return this;
},

/**
  Called whenever you try to get or set an undefined property.

  This is a generic property handler.  If you define it, it will be called
  when the named property is not yet set in the object.  The default does
  nothing.

  @param {String} key the key that was requested
  @param {Object} value The value if called as a setter, undefined if called as a getter.
  @returns {Object} The new value for key.
*/
unknownProperty: function (key, value) {
  if (value !== undefined) { this[key] = value; }
  return value;
},

/**
  Begins a grouping of property changes.

  You can use this method to group property changes so that notifications
  will not be sent until the changes are finished.  If you plan to make a
  large number of changes to an object at one time, you should call this
  method at the beginning of the changes to suspend change notifications.
  When you are done making changes, call endPropertyChanges() to allow
  notification to resume.

  @returns {SC.Observable}
*/
beginPropertyChanges: function () {
  this._kvo_changeLevel = this._kvo_changeLevel + 1;
  return this;
},

/**
  Ends a grouping of property changes.

  You can use this method to group property changes so that notifications
  will not be sent until the changes are finished.  If you plan to make a
  large number of changes to an object at one time, you should call
  beginPropertyChanges() at the beginning of the changes to suspend change
  notifications. When you are done making changes, call this method to allow
  notification to resume.

  @returns {SC.Observable}
*/
endPropertyChanges: function () {
  this._kvo_changeLevel = (this._kvo_changeLevel || 1) - 1;
  var level = this._kvo_changeLevel, changes = this._kvo_changes;
  if ((level <= 0) && changes && (changes.length > 0) && !SC.Observers.isObservingSuspended) {
    this._notifyPropertyObservers();
  }
  return this;
},

/**
  Notify the observer system that a property is about to change.

  Sometimes you need to change a value directly or indirectly without
  actually calling get() or set() on it.  In this case, you can use this
  method and propertyDidChange() instead.  Calling these two methods
  together will notify all observers that the property has potentially
  changed value.

  Note that you must always call propertyWillChange and propertyDidChange as
  a pair.  If you do not, it may get the property change groups out of order
  and cause notifications to be delivered more often than you would like.

  @param {String} key The property key that is about to change.
  @returns {SC.Observable}
*/
propertyWillChange: function (key) {
  return this;
},

/**
  Notify the observer system that a property has just changed.

  Sometimes you need to change a value directly or indirectly without
  actually calling get() or set() on it.  In this case, you can use this
  method and propertyWillChange() instead.  Calling these two methods
  together will notify all observers that the property has potentially
  changed value.

  Note that you must always call propertyWillChange and propertyDidChange as
  a pair. If you do not, it may get the property change groups out of order
  and cause notifications to be delivered more often than you would like.

  @param {String} key The property key that has just changed.
  @param {Object} value The new value of the key.  May be null.
  @param {Boolean} _keepCache Private property
  @returns {SC.Observable}
*/
propertyDidChange: function (key, value, _keepCache) {
  this._kvo_revision = this._kvo_revision + 1;
  var level = this._kvo_changeLevel,
      cachedep, idx, dfunc, func;

  //@if(debug)
  var log = SC.LOG_OBSERVERS && (this.LOG_OBSERVING !== NO);
  //@endif

  // If any dependent keys contain this property in their path,
  // invalidate the cache of the computed property and re-setup chain with
  // new value.
  var chains = this._kvo_property_chains;
  if (chains) {
    var keyChains = chains[key];

    if (keyChains) {
      this.beginPropertyChanges();
      keyChains = SC.clone(keyChains);
      keyChains.forEach(function (chain) {
        // Invalidate the property that depends on the changed key.
        chain.notifyPropertyDidChange();
      });
      this.endPropertyChanges();
    }
  }

  var cache = this._kvo_cache;
  if (cache) {

    // clear any cached value
    if (!_keepCache) {
      func = this[key];
      if (func && func.isProperty) {
        cache[func.cacheKey] = cache[func.lastSetValueKey] = undefined;
      }
    }

    if (this._kvo_cacheable) {
      // if there are any dependent keys and they use caching, then clear the
      // cache.  This is the same code as is in set.  It is inlined for perf.
      cachedep = this._kvo_cachedep;
      if (!cachedep || (cachedep = cachedep[key]) === undefined) {
        cachedep = this._kvo_computeCachedDependentsFor(key);
      }

      if (cachedep) {
        idx = cachedep.length;
        while (--idx >= 0) {
          dfunc = cachedep[idx];
          cache[dfunc.cacheKey] = cache[dfunc.lastSetValueKey] = undefined;
        }
      }
    }
  }

  // save in the change set if queuing changes
  var suspended = SC.Observers.isObservingSuspended;
  if ((level > 0) || suspended) {
    var changes = this._kvo_changes;
    if (!changes) changes = this._kvo_changes = SC.CoreSet.create();
    changes.add(key);

    if (suspended) {
      //@if(debug)
      if (log) console.log("%@%@: will not notify observers because observing is suspended".fmt(SC.KVO_SPACES, this));
      //@endif
      SC.Observers.objectHasPendingChanges(this);
    }

  // otherwise notify property observers immediately
  } else {
    this._notifyPropertyObservers(key);
  }

  return this;
},

// ..........................................
// DEPENDENT KEYS
//

/**
  Use this to indicate that one key changes if other keys it depends on
  change.  Pass the key that is dependent and additional keys it depends
  upon.  You can either pass the additional keys inline as arguments or
  in a single array.

  You generally do not call this method, but instead pass dependent keys to
  your property() method when you declare a computed property.

  You can call this method during your init to register the keys that should
  trigger a change notification for your computed properties.

  @param {String} key the dependent key
  @param {Array|String} dependentKeys one or more dependent keys
  @returns {Object} this
*/
registerDependentKey: function (key, dependentKeys) {
  var dependents      = this._kvo_dependents,
    // chainDependents = this._kvo_chain_dependents,
    keys, idx, lim, dep, queue;

  // normalize input.
  if (typeof dependentKeys === "object" && (dependentKeys instanceof Array)) {
    keys = dependentKeys;
    lim  = 0;
  } else {
    keys = arguments;
    lim  = 1;
  }
  idx  = keys.length;

  // define dependents if not defined already.
  if (!dependents) this._kvo_dependents = dependents = {};

  // for each key, build array of dependents, add this key...
  // note that we ignore the first argument since it is the key...
  while (--idx >= lim) {
    dep = keys[idx];

    if (dep.indexOf('.') >= 0) {
      SC._PropertyChain.createChain(dep, this, key).activate();
    } else {
      // add dependent key to dependents array of key it depends on
      queue = dependents[dep];
      if (!queue) { queue = dependents[dep] = []; }
      queue.push(key);
    }
  }
},

/** @private
  Register a property chain so that dependent keys can be invalidated
  when a property on this object changes.

  @param {String} property the property on this object that invalidates the chain
  @param {SC._PropertyChain} chain the chain to notify
*/
registerDependentKeyWithChain: function (property, chain) {
  var chains = this._chainsFor(property);
  chains.add(chain);
},

/** @private
  Removes a property chain from the object.

  @param {String} property the property on this object that invalidates the chain
  @param {SC._PropertyChain} chain the chain to notify
*/
removeDependentKeyWithChain: function (property, chain) {
  var chains = this._chainsFor(property);
  chains.remove(chain);

  if (chains.get('length') === 0) {
    delete this._kvo_property_chains[property];
  }
},

/** @private
  Returns an instance of SC.CoreSet in which to save SC._PropertyChains.

  @param {String} property the property associated with the SC._PropertyChain
  @returns {SC.CoreSet}
*/
_chainsFor: function (property) {
  this._kvo_property_chains = this._kvo_property_chains || {};
  var chains = this._kvo_property_chains[property] || SC.CoreSet.create();
  this._kvo_property_chains[property] = chains;

  return chains;
},

/** @private

  Helper method used by computeCachedDependents.  Just loops over the
  array of dependent keys.  If the passed function is cacheable, it will
  be added to the queue.  Also, recursively call on each keys dependent
  keys.

  @param {Array} queue the queue to add functions to
  @param {Array} keys the array of dependent keys for this key
  @param {Hash} dependents the _kvo_dependents cache
  @param {SC.Set} seen already seen keys
  @returns {void}
*/
_kvo_addCachedDependents: function (queue, keys, dependents, seen) {
  var idx = keys.length,
      func, key, deps;

  while (--idx >= 0) {
    key  = keys[idx];
    seen.add(key);

    // if the value for this key is a computed property, then add it to the
    // set if it is cacheable, and process any of its dependent keys also.
    func = this[key];
    if (func && (func instanceof Function) && func.isProperty) {
      if (func.isCacheable) queue.push(func); // handle this func
      if ((deps = dependents[key]) && deps.length > 0) { // and any dependents
        this._kvo_addCachedDependents(queue, deps, dependents, seen);
      }
    }
  }

},

/** @private

  Called by set() whenever it needs to determine which cached dependent
  keys to clear.  Recursively searches dependent keys to determine all
  cached property directly or indirectly affected.

  The return value is also saved for future reference

  @param {String} key the key to compute
  @returns {Array}
*/
_kvo_computeCachedDependentsFor: function (key) {
  var cached     = this._kvo_cachedep,
      dependents = this._kvo_dependents,
      keys       = dependents ? dependents[key] : null,
      queue, seen;
  if (!cached) cached = this._kvo_cachedep = {};

  // if there are no dependent keys, then just set and return null to avoid
  // this mess again.
  if (!keys || keys.length === 0) return cached[key] = null;

  // there are dependent keys, so we need to do the work to find out if
  // any of them or their dependent keys are cached.
  queue = cached[key] = [];
  seen  = SC._TMP_SEEN_SET = (SC._TMP_SEEN_SET || SC.CoreSet.create());
  seen.add(key);
  this._kvo_addCachedDependents(queue, keys, dependents, seen);
  seen.clear(); // reset

  if (queue.length === 0) queue = cached[key] = null; // turns out nothing
  return queue;
},

// ..........................................
// OBSERVERS
//

_kvo_for: function (kvoKey, type) {
  var ret = this[kvoKey];

  if (!this._kvo_cloned) this._kvo_cloned = {};

  // if the item does not exist, create it.  Unless type is passed,
  // assume array.
  if (!ret) {
    ret = this[kvoKey] = (type === undefined) ? [] : type.create();
    this._kvo_cloned[kvoKey] = YES;

  // if item does exist but has not been cloned, then clone it.  Note
  // that all types must implement copy().0
  } else if (!this._kvo_cloned[kvoKey]) {
    ret = this[kvoKey] = ret.copy();
    this._kvo_cloned[kvoKey] = YES;
  }

  return ret;
},

/**
  Adds an observer on a property.

  This is the core method used to register an observer for a property.

  Once you call this method, anytime the key's value is set, your observer
  will be notified.  Note that the observers are triggered anytime the
  value is set, regardless of whether it has actually changed.  Your
  observer should be prepared to handle that.

  You can also pass an optional context parameter to this method.  The
  context will be passed to your observer method whenever it is triggered.
  Note that if you add the same target/method pair on a key multiple times
  with different context parameters, your observer will only be called once
  with the last context you passed.

  Observer Methods
  ---

  Observer methods you pass should generally have the following signature if
  you do not pass a "context" parameter:

        fooDidChange: function (sender, key, value, rev);

  The sender is the object that changed.  The key is the property that
  changes.  The value property is currently reserved and unused.  The rev
  is the last property revision of the object when it changed, which you can
  use to detect if the key value has really changed or not.

  If you pass a "context" parameter, the context will be passed before the
  revision like so:

        fooDidChange: function (sender, key, value, context, rev);

  Usually you will not need the value, context or revision parameters at
  the end.  In this case, it is common to write observer methods that take
  only a sender and key value as parameters or, if you aren't interested in
  any of these values, to write an observer that has no parameters at all.

  @param {String} key the key to observer
  @param {Object} target the target object to invoke
  @param {String|Function} method the method to invoke.
  @param {Object} context optional context
  @returns {SC.Object} self
*/
addObserver: function (key, target, method, context) {
  var kvoKey, chain;

  // normalize.  if a function is passed to target, make it the method.
  if (method === undefined) {
    method = target;
    target = this;
  }
  if (!target) target = this;

  if (typeof method === "string") method = target[method];
  if (!method) throw new Error("You must pass a method to addObserver()");

  // Normalize key...
  key = key.toString();
  if (key.indexOf('.') >= 0) {

    // create the chain and save it for later so we can tear it down if
    // needed.
    chain = SC._ChainObserver.createChain(this, key, target, method, context);
    chain.masterTarget = target;
    chain.masterMethod = method;

    // Save in set for chain observers.
    this._kvo_for(SC.keyFor('_kvo_chains', key)).push(chain);

  // Create observers if needed...
  } else {

    // Special case to support reduced properties.  If the property
    // key begins with '@' and its value is unknown, then try to get its
    // value.  This will configure the dependent keys if needed.
    if ((this[key] === undefined) && (key.indexOf('@') === 0)) {
      this.get(key);
    }

    if (target === this) target = null; // use null for observers only.
    kvoKey = SC.keyFor('_kvo_observers', key);
    this._kvo_for(kvoKey, SC.ObserverSet).add(target, method, context);
    this._kvo_for('_kvo_observed_keys', SC.CoreSet).add(key);
  }

  if (this.didAddObserver) this.didAddObserver(key, target, method);
  return this;
},

/**
  Remove an observer you have previously registered on this object.  Pass
  the same key, target, and method you passed to addObserver() and your
  target will no longer receive notifications.

  @param {String} key the key to observer
  @param {Object} target the target object to invoke
  @param {String|Function} method the method to invoke.
  @returns {SC.Observable} receiver
*/
removeObserver: function (key, target, method) {

  var kvoKey, chains, chain, observers, idx;

  // normalize.  if a function is passed to target, make it the method.
  if (method === undefined) {
    method = target;
    target = this;
  }
  if (!target) target = this;

  if (typeof method === "string") method = target[method];
  if (!method) throw new Error("You must pass a method to removeObserver()");

  // if the key contains a '.', this is a chained observer.
  key = key.toString();
  if (key.indexOf('.') >= 0) {

    // try to find matching chains
    kvoKey = SC.keyFor('_kvo_chains', key);
    if (chains = this[kvoKey]) {

      // if chains have not been cloned yet, do so now.
      chains = this._kvo_for(kvoKey);

      // remove any chains
      idx = chains.length;
      while (--idx >= 0) {
        chain = chains[idx];
        if (chain && (chain.masterTarget === target) && (chain.masterMethod === method)) {
          chains[idx] = chain.destroyChain();
        }
      }
    }

  // otherwise, just like a normal observer.
  } else {
    if (target === this) target = null; // use null for observers only.
    kvoKey = SC.keyFor('_kvo_observers', key);
    if (observers = this[kvoKey]) {
      // if observers have not been cloned yet, do so now
      observers = this._kvo_for(kvoKey);
      observers.remove(target, method);

      // Remove the key when no members remain.
      if (observers.getMembers().length === 0) {
        this._kvo_for('_kvo_observed_keys', SC.CoreSet).remove(key);
      }
    }
  }

  if (this.didRemoveObserver) this.didRemoveObserver(key, target, method);
  return this;
},

/**
  Returns YES if the object currently has observers registered for a
  particular key.  You can use this method to potentially defer performing
  an expensive action until someone begins observing a particular property
  on the object.

  Optionally, you may pass a target and method to check for the
  presence of a particular observer. You can use this to avoid creating
  duplicate observers in situations where that's likely.

  @param {String} key key to check
  @param {Object} [target] the target that the observer uses
  @param {Function|String} [method]) the method on the target that the observer uses
  @returns {Boolean}
*/
hasObserverFor: function (key, target, method) {
  SC.Observers.flush(this); // hookup as many observers as possible.

  var observers = this[SC.keyFor('_kvo_observers', key)],
      chains = this._kvo_for(SC.keyFor('_kvo_chains', key)),
      locals = this[SC.keyFor('_kvo_local', key)],
      isChain = key.indexOf('.') >= 0;

  // Fast path: no target/method.
  if (target === undefined) {
    if (isChain) {
      if (chains && chains.length > 0) return YES;
    } else {
      // Found locally.
      if (locals && locals.length > 0) return YES;
      if (observers && observers.getMembers().length > 0) return YES;
    }
    return NO;

  // Slow path: target/method.
  } else {
    if (method === undefined) {
      method = target;
      target = this;
    }
    if (typeof method === "string") method = target[method];
    if (!method) throw new Error("Developer Error: If present, the `method` argument of hasObserverFor must be (or refer to) a function.");

    // Declare our iterators.
    var i, len;

    // Check remote chains.
    if (isChain) {
      if (!chains || !chains.length) return NO;
      len = chains.length;
      for (i = 0; i < len; i++) {
        if (chains[i].masterTarget === target && chains[i].masterMethod === method) return YES;
      }
      return NO;

    // Check locals.
    } else if (target === this) {
      if (!locals) return NO;
      len = locals.length;
      for (i = 0; i < len; i++) {
        if (this[locals[i]] === method) return YES;
      }
      return NO;

    // Check remotes.
    } else {
      if (!observers || !observers.members) return NO;

      len = observers.members.length;
      var member;
      for (i = 0; i < len; i++) {
        member = observers.members[i];
        // If this is a non-chained observer, the first item is the target and the second is the method.
        if (member[0] === target && member[1] === method) return YES;
      }
      return NO;
    }
    // TODO: Remote chains.
  }
},

/**
  This method will register any observers and computed properties saved on
  the object.  Normally you do not need to call this method yourself.  It
  is invoked automatically just before property notifications are sent and
  from the init() method of SC.Object.  You may choose to call this
  from your own initialization method if you are using SC.Observable in
  a non-SC.Object-based object.

  This method looks for several private variables, which you can setup,
  to initialize:

    - _observers: this should contain an array of key names for observers
      you need to configure.

    - _bindings: this should contain an array of key names that configure
      bindings.

    - _properties: this should contain an array of key names for computed
      properties.

  @returns {Object} this
*/
initObservable: function () {
  if (this._observableInited) return;
  this._observableInited = YES;

  var loc, keys, key, value, observer, propertyPaths, propertyPathsLength,
      len, ploc, path, propertyKey, keysLen;

  // Loop through observer functions and register them
  if (keys = this._observers) {
    len = keys.length;
    for (loc = 0; loc < len; loc++) {
      key = keys[loc];
      observer = this[key];
      propertyPaths = observer.propertyPaths;
      propertyPathsLength = (propertyPaths) ? propertyPaths.length : 0;
      for (ploc = 0 ; ploc < propertyPathsLength; ploc++) {
        path = propertyPaths[ploc];
        this.addObservesHandler(observer, path);
      }
    }
  }

  // Add Bindings
  this.bindings = []; // will be filled in by the bind() method.
  if (keys = this._bindings) {
    for (loc = 0, keysLen = keys.length; loc < keysLen; loc++) {
      // get propertyKey
      key = keys[loc];
      value = this[key];
      propertyKey = key.slice(0, -7); // contentBinding => content

      // Replace the short form property with the new binding object.
      this[key] = this.bind(propertyKey, value);
    }
  }

  // Add Properties
  if (keys = this._properties) {
    for (loc = 0, keysLen = keys.length; loc < keysLen; loc++) {
      key = keys[loc];
      if (value = this[key]) {

        // activate cacheable only if needed for perf reasons
        if (value.isCacheable) this._kvo_cacheable = YES;

        // register dependent keys
        if (value.dependentKeys && (value.dependentKeys.length > 0)) {
          this.registerDependentKey(key, value.dependentKeys);
        }
      }
    }
  }

  // Clean up these properties once they have been used.
  delete this._bindings;
  delete this._properties;

  return this;
},

/**
  This method will destroy the observable.

  @returns {Object} this
*/
destroyObservable: function () {
  var key, keys,
    len,
    observer,
    path,
    propertyPaths,
    propertyPathsLength;

  // Destroy bindings
  this.bindings.invoke('destroy');
  delete this.bindings;

  // Loop through observer functions and remove them
  if (keys = this._observers) {
    len = keys.length;
    for (var loc = 0; loc < len; loc++) {
      key = keys[loc];
      observer = this[key];
      propertyPaths = observer.propertyPaths;
      propertyPathsLength = (propertyPaths) ? propertyPaths.length : 0;

      for (var ploc = 0; ploc < propertyPathsLength; ploc++) {
        path = propertyPaths[ploc];
        this.removeObservesHandler(observer, path);
      }
    }
  }

  delete this._observers;

  return this;
},

/**
  Will add an observes handler to this object for a given property path.

  In most cases, the path provided is relative to this object. However,
  if the path begins with a capital character then the path is considered
  relative to the window object.

  @param {Function} observer the function on this object that will be
    notified of changes
  @param {String} path a property path string
  @return {Object} returns this
*/
addObservesHandler: function (observer, path) {
  this._configureObservesHandler(SC.OBSERVES_HANDLER_ADD, observer, path);
  return this;
},

/**
  Will remove an observes handler from this object for a given property path.

  In most cases, the path provided is relative to this object. However,
  if the path begins with a capital character then the path is considered
  relative to the window object.

  @param {Function} observer the function on this object that will be
    notified of changes
  @param {String} path a property path string
  @return {Object} returns this
*/
removeObservesHandler: function (observer, path) {
  this._configureObservesHandler(SC.OBSERVES_HANDLER_REMOVE, observer, path);
  return this;
},

/** @private

  Used to either add or remove an observer handler on this object
  for a given property path.

  In most cases, the path provided is relative to this object. However,
  if the path begins with a capital character then the path is considered
  relative to the window object.

  You must supply an action that is to be performed by this method. The
  action can either be `SC.OBSERVES_HANDLER_ADD` or `SC.OBSERVES_HANDLER_REMOVE`.

  @param {Function} observer the function on this object that will be
    notified of changes
  @param {String} path a property path string
  @param {String} path a dot-notation property path string
*/
_configureObservesHandler: function (action, observer, path) {
  var dotIndex, root;

  switch (action) {
  case SC.OBSERVES_HANDLER_ADD:
    action = "addObserver";
    break;
  case SC.OBSERVES_HANDLER_REMOVE:
    action = "removeObserver";
    break;
  default:
    throw new Error("invalid action provided: " + action);
  }

  dotIndex = path.indexOf('.');

  if (dotIndex < 0) {
    this[action](path, this, observer);
  } else if (path.indexOf('*') === 0) {
    this[action](path.slice(1), this, observer);
  } else {
    root = null;

    if (dotIndex === 0) {
      root = this;
      path = path.slice(1);
    } else if (dotIndex === 4 && path.slice(0, 5) === 'this.') {
      root = this;
      path = path.slice(5);
    } else if (dotIndex < 0 && path.length === 4 && path === 'this') {
      root = this;
      path = '';
    } else if (dotIndex > 0 && path[0] === path.charAt(0).toLowerCase()) {
      // if the first character for the given path is lower case
      // then we assume the path is relative to this
      root = this;
    }

    SC.Observers[action](path, this, observer, root);
  }
},

// ..........................................
// NOTIFICATION
//

/**
  Returns an array with all of the observers registered for the specified
  key.  This is intended for debugging purposes only.  You generally do not
  want to rely on this method for production code.

  @param {String} key the key to evaluate
  @returns {Array} array of Observer objects, describing the observer.
*/
observersForKey: function (key) {
  SC.Observers.flush(this); // hookup as many observers as possible.

  var observers = this[SC.keyFor('_kvo_observers', key)];
  return observers ? observers.getMembers() : [];
},

/** @private
  This private method actually notifies the observers for any keys in the observer queue.  If you
  pass a key it will be added to the queue.
*/
_notifyPropertyObservers: function (key) {
  // Ensure that this object has been initialized.
  if (!this._observableInited) this.initObservable();

  SC.Observers.flush(this); // hookup as many observers as possible.

  var observers, changes, dependents, starObservers, idx, keys, rev,
      members, membersLength, member, memberLoc, target, method, loc, func,
      context, spaces, cache;

  //@if(debug)
  var log = SC.LOG_OBSERVERS && this.LOG_OBSERVING !== NO;
  if (log) {
    spaces = SC.KVO_SPACES = (SC.KVO_SPACES || '') + '  ';
    console.log('%@%@: notifying observers after change to key "%@"'.fmt(spaces, this, key));
  }
  //@endif

  // Get any starObservers -- they will be notified of all changes.
  starObservers = this['_kvo_observers_*'];

  // prevent notifications from being sent until complete
  this._kvo_changeLevel = this._kvo_changeLevel + 1;

  // keep sending notifications as long as there are changes
  while (((changes = this._kvo_changes) && (changes.length > 0)) || key) {

    // increment revision
    rev = ++this.propertyRevision;

    // save the current set of changes and swap out the kvo_changes so that
    // any set() calls by observers will be saved in a new set.
    if (!changes) changes = SC.CoreSet.create();
    this._kvo_changes = null;

    // Add the passed key to the changes set.  If a '*' was passed, then
    // add all keys in the observers to the set...
    // once finished, clear the key so the loop will end.
    if (key === '*') {
      changes.add('*');
      changes.addEach(this._kvo_for('_kvo_observed_keys', SC.CoreSet));

    } else if (key) {
      changes.add(key);
    }

    // Now go through the set and add all dependent keys...
    dependents = this._kvo_dependents;
    if (dependents) {

      // NOTE: each time we loop, we check the changes length, this
      // way any dependent keys added to the set will also be evaluated...
      for (idx = 0; idx < changes.length; idx++) {
        key = changes[idx];
        keys = dependents[key];

        // for each dependent key, add to set of changes.  Also, if key
        // value is a cacheable property, clear the cached value...
        if (keys && (loc = keys.length)) {
          //@if(debug)
          if (log) {
            console.log("%@...including dependent keys for %@: %@".fmt(spaces, key, keys));
          }
          //@endif
          cache = this._kvo_cache;
          if (!cache) cache = this._kvo_cache = {};
          while (--loc >= 0) {
            changes.add(key = keys[loc]);
            if (func = this[key]) {
              this[func.cacheKey] = undefined;
              cache[func.cacheKey] = cache[func.lastSetValueKey] = undefined;
            } // if (func=)
          } // while (--loc)
        } // if (keys &&
      } // for(idx...
    } // if (dependents...)

    // now iterate through all changed keys and notify observers.
    while (changes.length > 0) {
      key = changes.pop(); // the changed key

      // find any observers and notify them...
      observers = this[SC.keyFor('_kvo_observers', key)];

      if (observers) {
        // We need to clone the 'members' structure here in case any of the
        // observers we're about to notify happen to remove observers for
        // this key, which would mutate the structure underneath us.
        // (Cloning it rather than mutating gives us a clear policy:  if you
        // were registered as an observer at the time notification begins,
        // you will be notified, regardless of whether you're removed as an
        // observer during that round of notification.  Similarly, if you're
        // added as an observer during the notification round by another
        // observer, you will not be notified until the next time.)
        members = observers.getMembers();
        membersLength = members.length;

        for (memberLoc = 0; memberLoc < membersLength; memberLoc++) {
          member = members[memberLoc];

          if (member[3] === rev) continue; // skip notified items.

          if (!member[1]) console.log(member);

          target = member[0] || this;
          method = member[1];
          context = member[2];
          member[3] = rev;

          //@if(debug)
          if (log) console.log('%@...firing observer on %@ for key "%@"'.fmt(spaces, target, key));
          //@endif
          if (context !== undefined) {
            method.call(target, this, key, null, context, rev);
          } else {
            method.call(target, this, key, null, rev);
          }
        }
      }

      // look for local observers.  Local observers are added by SC.Object
      // as an optimization to avoid having to add observers for every
      // instance when you are just observing your local object.
      members = this[SC.keyFor('_kvo_local', key)];
      if (members) {
        // Note:  Since, unlike above, we don't expect local observers to be
        //        removed in general, we will not clone 'members'.
        membersLength = members.length;
        for (memberLoc = 0; memberLoc < membersLength; memberLoc++) {
          member = members[memberLoc];
          method = this[member]; // try to find observer function
          if (method) {
            //@if(debug)
            if (log) console.log('%@...firing local observer %@.%@ for key "%@"'.fmt(spaces, this, member, key));
            //@endif

            method.call(this, this, key, null, rev);
          }
        }
      }

      // if there are starObservers, do the same thing for them
      if (starObservers && key !== '*') {
        // We clone the structure per the justification, above, for regular
        // observers.
        members = starObservers.getMembers();
        membersLength = members.length;
        for (memberLoc = 0; memberLoc < membersLength; memberLoc++) {
          member = members[memberLoc];
          target = member[0] || this;
          method = member[1];
          context = member[2];

          //@if(debug)
          if (log) console.log('%@...firing * observer on %@ for key "%@"'.fmt(spaces, target, key));
          //@endif
          if (context !== undefined) {
            method.call(target, this, key, null, context, rev);
          } else {
            method.call(target, this, key, null, rev);
          }
        }
      }

      // if there is a default property observer, call that also
      if (this.propertyObserver) {
        //@if(debug)
        if (log) console.log('%@...firing %@.propertyObserver for key "%@"'.fmt(spaces, this, key));
        //@endif
        this.propertyObserver(this, key, null, rev);
      }
    } // while(changes.length>0)

    // changes set should be empty. release it for reuse
    if (changes) changes.destroy();

    // key is no longer needed; clear it to avoid infinite loops
    key = null;

  } // while (changes)

  // done with loop, reduce change level so that future sets can resume
  this._kvo_changeLevel = (this._kvo_changeLevel || 1) - 1;

  //@if(debug)
  if (log) SC.KVO_SPACES = spaces.slice(0, -2);
  //@endif

  return YES; // finished successfully
},

// ..........................................
// BINDINGS
//

/**
  Manually add a new binding to an object.  This is the same as doing
  the more familiar propertyBinding: 'property.path' approach.

  @param {String} toKey the key to bind to
  @param {Object} target target or property path to bind from
  @param {String|Function} method method for target to bind from
  @returns {SC.Binding} new binding instance
*/
bind: function (toKey, target, method) {
  var binding, pathType;

  //@if(debug)
  // Developer support.
  if (!target) {
    throw new Error("Developer Error: Attempt to bind key `%@` to null or undefined target".fmt(toKey));
  }
  //@endif

  // normalize...
  if (method !== undefined) target = [target, method];

  pathType = typeof target;

  // if a string or array (i.e. tuple) is passed, convert this into a
  // binding.  If a binding default was provided, use that.
  if (pathType === "string" || (pathType === "object" && (target instanceof Array))) {
    binding = this[toKey + 'BindingDefault'] || SC.Binding;
    binding = binding.beget().from(target);
  } else {
    // If a binding object was provided, clone it so that it gets
    // connected again if the original example binding was already
    // connected.
    binding = target.beget();
  }

  // finish configuring the binding and then connect it.
  binding = binding.to(toKey, this).connect();
  this.bindings.push(binding);

  return binding;
},

/**
  didChangeFor is a very important method which allows you to tell whether
  a property or properties have changed.

  The key to using didChangeFor is to pass a unique string as the first argument,
  which signals, "Has anything changed since the last time this was called with
  this unique key?" The string can be anything you want, as long as it's unique
  and stays the same from call to call.

  After the key argument, you can pass as many property arguments as you like;
  didChangeFor will only return `true` if any of those properties have changed
  since the last call.

  For example, in your view's update method, you might want to gate DOM changes
  (generally a slow operation) on whether the root values have changed. You might
  ask the following:

      if (this.didChangeFor('updateOnDisplayValue', 'displayValue')) {
        // Update the DOM.
      }

  In another method on the same view, you might send an event if that same value
  has changed:

      if (this.didChangeFor('otherMethodDisplayValue', 'displayValue')) {
        // Send a statechart action.
      }

  Each call will correctly return whether the property has changed since the last
  time displayDidChange was called *with that key*. The following sequence of calls
  will return the following values:

    - this.set('displayValue', 'value1');
    - this.didChangeFor('updateOnDisplayValue', 'displayValue');
    > true;
    - this.didChangeFor('updateOnDisplayValue', 'displayValue');
    > false;
    - this.didChangeFor('otherMethodDisplayValue', 'displayValue');
    > true;
    - this.set('displayValue', 'value2');
    - this.didChangeFor('updateOnDisplayValue', 'displayValue');
    > true;
    - this.didChangeFor('updateOnDisplayValue', 'displayValue');
    > false;
    - this.didChangeFor('updateOnDisplayValue', 'displayValue');
    > false;
    - this.didChangeFor('otherMethodDisplayValue', 'displayValue');
    > false;

  This method works by comparing property revision counts. Every time a
  property changes, an internal counter is incremented. When didChangeFor is
  invoked, the current revision count of the property is compared to the
  revision count from the last time this method was called.

  @param {String|Object} context a unique identifier
  @param {String…} propertyNames one or more property names
*/
didChangeFor: function (context) {
  var valueCache, revisionCache, seenValues, seenRevisions, ret,
      currentRevision, idx, key, value;
  context = SC.hashFor(context); // get a hash key we can use in caches.

  // setup caches...
  valueCache = this._kvo_didChange_valueCache;
  if (!valueCache) valueCache = this._kvo_didChange_valueCache = {};
  revisionCache = this._kvo_didChange_revisionCache;
  if (!revisionCache) revisionCache = this._kvo_didChange_revisionCache = {};

  // get the cache of values and revisions already seen in this context
  seenValues = valueCache[context] || {};
  seenRevisions = revisionCache[context] || {};

  // prepare to loop!
  ret = false;
  currentRevision = this._kvo_revision;
  idx = arguments.length;
  while (--idx >= 1) {  // NB: loop only to 1 to ignore context arg.
    key = arguments[idx];

    // has the kvo revision changed since the last time we did this?
    if (seenRevisions[key] != currentRevision) {
      // yes, check the value with the last seen value
      value = this.get(key);
      if (seenValues[key] !== value) {
        ret = true; // did change!
        seenValues[key] = value;
      }
    }
    seenRevisions[key] = currentRevision;
  }

  valueCache[context] = seenValues;
  revisionCache[context] = seenRevisions;
  return ret;
},

/**
  Sets the property only if the passed value is different from the
  current value.  Depending on how expensive a get() is on this property,
  this may be more efficient.

  NOTE: By default, the set() method will not set the value unless it has
  changed. However, this check can skipped by setting .property().idempotent(NO)
  setIfChanged() may be useful in this case.

  @param {String|Hash} key the key to change
  @param {Object} value the value to change
  @returns {SC.Observable}
*/
setIfChanged: function (key, value) {
  if (value === undefined && SC.typeOf(key) === SC.T_HASH) {
    var hash = key;

    for (key in hash) {
      if (!hash.hasOwnProperty(key)) continue;
      this.setIfChanged(key, hash[key]);
    }

    return this;
  }

  return (this.get(key) !== value) ? this.set(key, value) : this;
},

/**
  Navigates the property path, returning the value at that point.

  If any object in the path is undefined, returns undefined.
  @param {String} path The property path you want to retrieve
*/
getPath: function (path) {
  var tuple = SC.tupleForPropertyPath(path, this);
  if (tuple === null || tuple[0] === null) return undefined;
  return SC.get(tuple[0], tuple[1]);
},

/**
  Navigates the property path, finally setting the value.

  @param {String} path the property path to set
  @param {Object} value the value to set
  @returns {SC.Observable}
*/
setPath: function (path, value) {
  if (path.indexOf('.') >= 0) {
    var tuple = SC.tupleForPropertyPath(path, this);
    if (!tuple || !tuple[0]) return null;
    tuple[0].set(tuple[1], value);
  } else this.set(path, value); // shortcut
  return this;
},

/**
  Navigates the property path, finally setting the value but only if
  the value does not match the current value.  This will avoid sending
  unnecessary change notifications.

  @param {String} path the property path to set
  @param {Object} value the value to set
  @returns {Object} this
*/
setPathIfChanged: function (path, value) {
  if (path.indexOf('.') >= 0) {
    var tuple = SC.tupleForPropertyPath(path, this);
    if (!tuple || !tuple[0]) return null;
    if (tuple[0].get(tuple[1]) !== value) {
      tuple[0].set(tuple[1], value);
    }
  } else this.setIfChanged(path, value); // shortcut
  return this;
},

/**
  Convenience method to get an array of properties.

  Pass in multiple property keys or an array of property keys.  This
  method uses getPath() so you can also pass key paths.

  @returns {Array} Values of property keys.
*/
getEach: function () {
  var ret = [], idx, idxLen;

  for (idx = 0, idxLen = arguments.length; idx < idxLen; idx++) {
    ret[ret.length] = this.getPath(arguments[idx]);
  }
  return ret;
},

/**
  Increments the value of a property.

  @param {String} key property name
  @param {Number} increment the amount to increment (optional)
  @returns {Number} new value of property
*/
incrementProperty: function (key, increment) {
  if (!increment) increment = 1;
  this.set(key, (this.get(key) || 0) + increment);
  return this.get(key);
},

/**
  Decrements the value of a property.

  @param {String} key property name
  @param {Number} increment the amount to decrement (optional)
  @returns {Number} new value of property
*/
decrementProperty: function (key, increment) {
  if (!increment) increment = 1;
  this.set(key, (this.get(key) || 0) - increment);
  return this.get(key);
},

/**
  Inverts a property.  Property should be a bool.

  @param {String} key property name
  @param {Object} value optional parameter for "true" value
  @param {Object} alt optional parameter for "false" value
  @returns {Object} new value
*/
toggleProperty: function (key, value, alt) {
  if (value === undefined) value = true;
  if (alt === undefined) alt = false;
  value = (this.get(key) == value) ? alt : value;
  this.set(key, value);
  return this.get(key);
},

/**
  Convenience method to call propertyWillChange/propertyDidChange.

  Sometimes you need to notify observers that a property has changed value
  without actually changing this value.  In those cases, you can use this
  method as a convenience instead of calling propertyWillChange() and
  propertyDidChange().

  @param {String} key The property key that has just changed.
  @param {Object} value The new value of the key.  May be null.
  @returns {SC.Observable}
*/
notifyPropertyChange: function (key, value) {
  this.propertyWillChange(key);
  this.propertyDidChange(key, value);
  return this;
},

/**
  Notifies observers of all possible property changes.

  Sometimes when you make a major update to your object, it is cheaper to
  simply notify all observers that their property might have changed than
  to figure out specifically which properties actually did change.

  In those cases, you can simply call this method to notify all property
  observers immediately.  Note that this ignores property groups.

  @returns {SC.Observable}
*/
allPropertiesDidChange: function () {
  this._kvo_cache = null; //clear cached props
  this._notifyPropertyObservers('*');
  return this;
},

propertyRevision: 1

};

//@if(debug) /** @private used by addProbe/removeProbe. Debug mode only. */ SC.logChange = function logChange(target, key, value) {

console.log("CHANGE: %@[%@] => %@".fmt(target, key, target.get(key)));

}; //@endif

/**

Retrieves a property from an object, using get() if the
object implements SC.Observable.

@param  {Object}  object  the object to query
@param  {String}  key the property to retrieve

*/ SC.mixin(SC, {

get: function (object, key) {
  if (!object) return undefined;
  if (key === undefined) return this[object];
  if (object.get) return object.get(key);
  return object[key];
},

/**
  Retrieves a property from an object at a specified path, using get() if
  the object implements SC.Observable.

  @param  {Object}  object  the object to query
  @param  {String}  path the path to the property to retrieve
*/
getPath: function (object, path) {
  if (path === undefined) {
    path = object;
    object = window;
  }
  return SC.objectForPropertyPath(path, object);
}

});

// Make all Array's observable SC.mixin(Array.prototype, SC.Observable);