TurboStreamer
¶ ↑
TurboStreamer
gives you a simple DSL for generating JSON that beats massaging giant hash structures. This is particularly helpful when the generation process is fraught with conditionals and loops.
Jbuilder builds a Hash as it renders the template and once complete converts the Hash to JSON. TurboStreamer
on the other hand writes directly to the output as it is rendering the template. Because of this some of the magic cannot be done and requires a little more verboseness.
Examples¶ ↑
# app/views/message/show.json.streamer json.object! do json.content format_content(@message.content) json.extract! @message, :created_at, :updated_at json.author do json.object! do json.name @message.creator.name.familiar json.email_address @message.creator.email_address_with_name json.url url_for(@message.creator, format: :json) end end if current_user.admin? json.visitors calculate_visitors(@message) end json.tags do json.array! do @message.tags.each { |tag| json.child! tag } end end json.comments @message.comments, :content, :created_at json.attachments @message.attachments do |attachment| json.object! do json.filename attachment.filename json.url url_for(attachment) end end end
This will build the following structure:
{ "content": "<p>This is <i>serious</i> monkey business</p>", "created_at": "2011-10-29T20:45:28-05:00", "updated_at": "2011-10-29T20:45:28-05:00", "author": { "name": "David H.", "email_address": "'David Heinemeier Hansson' <david@heinemeierhansson.com>", "url": "http://example.com/users/1-david.json" }, "visitors": 15, "tags": ['public'], "comments": [ { "content": "Hello everyone!", "created_at": "2011-10-29T20:45:28-05:00" }, { "content": "To you my good sir!", "created_at": "2011-10-29T20:47:28-05:00" } ], "attachments": [ { "filename": "forecast.xls", "url": "http://example.com/downloads/forecast.xls" }, { "filename": "presentation.pdf", "url": "http://example.com/downloads/presentation.pdf" } ] }
To define attribute and structure names dynamically, use the set!
method:
json.object! do json.set! :author do json.object! do json.set! :name, 'David' end end end # => { "author": { "name": "David" } }
To merge existing hash or array to current context:
hash = { author: { name: "David" } } json.post do json.title "Merge HOWTO" json.merge! hash end # => "post": { "title": "Merge HOWTO", "author": { "name": "David" } }
Top level arrays can be handled directly. Useful for index and other collection actions.
json.array! @comments do |comment| next if comment.marked_as_spam_by?(current_user) json.object! do json.body comment.body json.author do json.first_name comment.author.first_name json.last_name comment.author.last_name end end end # => [ { "body": "great post...", "author": { "first_name": "Joe", "last_name": "Bloe" }} ]
You can also extract attributes from array directly.
# @people = People.all json.array! @people, :id, :name # => [ { "id": 1, "name": "David" }, { "id": 2, "name": "Jamie" } ]
You can either use TurboStreamer
stand-alone or directly as an ActionView template language. When required in Rails, you can create views ala show.json.streamer (the json is already yielded):
# Any helpers available to views are available to the builder json.object! do json.content format_content(@message.content) json.extract! @message, :created_at, :updated_at json.author do json.object! do json.name @message.creator.name.familiar json.email_address @message.creator.email_address_with_name json.url url_for(@message.creator, format: :json) end end if current_user.admin? json.visitors calculate_visitors(@message) end end
You can use partials as well. The following will render the file views/comments/_comments.json.streamer
, and set a local variable comments
with all this message's comments, which you can use inside the partial.
json.partial! 'comments/comments', comments: @message.comments
It's also possible to render collections of partials:
json.array! @posts, partial: 'posts/post', as: :post # or json.partial! 'posts/post', collection: @posts, as: :post # or json.partial! partial: 'posts/post', collection: @posts, as: :post # or json.comments @post.comments, partial: 'comment/comment', as: :comment
You can explicitly make TurboStreamer
object return null if you want:
json.extract! @post, :id, :title, :content, :published_at json.author do if @post.anonymous? json.null! # or json.nil! else json.object! do json.first_name @post.author_first_name json.last_name @post.author_last_name end end end
Fragment caching is supported, it uses Rails.cache
and works like caching in HTML templates:
json.object! do json.cache! ['v1', @person], expires_in: 10.minutes do json.extract! @person, :name, :age end end
You can also conditionally cache a block by using cache_if!
like this:
json.object! do json.cache_if! !admin?, ['v1', @person], expires_in: 10.minutes do json.extract! @person, :name, :age end end
The only caveat with caching is inside and object you must cache both the key and the value. You cannot just cache the value. For example:
json.boject! do json.key do json.cache! :key do json.value! 'Cache this.' end end end
Will error out, but can easily be rewritten as:
json.boject! do json.cache! :key do json.key do json.value! 'Cache this.' end end end
Keys can be auto formatted using key_format!
, this can be used to convert keynames from the standard ruby_format to camelCase:
json.key_format! camelize: :lower json.object! do json.first_name 'David' end # => { "firstName": "David" }
You can set this globally with the class method key_format
(from inside your environment.rb for example):
TurboStreamer.key_format camelize: :lower
Syntax Differences from Jbuilder¶ ↑
-
You must open JSON object or array if you want an object or array.
-
You can directly output a value with
json.value! value
, this will allow you to put a number, string, or other JSON value if you wish to not have an object or array. -
The call syntax has been removed (eg.
json.(@person, :name, :age)
) -
Caching inside of a object must cache both the key and the value.
Backends¶ ↑
Currently TurboStreamer
supports Wankel and Oj for JSON encoding.
By default TurboStreamer
will look for Oj
and Wankel
and use the first available option.
You can also set the encoder when initializing:
TurboStreamer.encode(encoder: :oj) # Or TurboStreamer.encode(encoder: :wankel) # You can also pass the class TurboStreamer.encode(encoder: TurboStreamer::WankelEncoder) # Or your own encoder TurboStreamer.encode(encoder: MyEncoder)
Setting the default encoder and options¶ ↑
If you need explicitly set the default:
TurboStreamer.set_default_encoder(:json, :oj)
You can also set default options to pass to the encoder if needed:
TurboStreamer.set_default_encoder(:json, :oj, buffer_size: 1_024)
You may also just set the default options for an encoder:
TurboStreamer.set_default_encoder_options(:oj, buffer_size: 2_048)
The idea was to also support MessagePack, hence requring the mime type when setting a default encoder.
Implementing MessagePack would require a bit of work as you would need a change in the protocol. We do not know how big an array or map/object will be when we start emitting it and MessagePack require we know it. It seems like a relatively small change, instead of a marker followed by number of lements there would be a start marker followed by the elements and then an end marker.
All backends must have the following functions:
-
key(string)
Output a map key -
value(value)
Output a value -
map_open
Open a object/map -
map_close
Close a object/map -
array_open
Open an Array -
array_close
Close an Array -
flush
Flush any buffers -
inject(string)
Inject a (usually cached) string into the output; instering any delimiters as needed. -
capture(&block)
Capture the output of the block (w/o any delimiters)
Special Thanks & Contributors¶ ↑
TurboStreamer
is a fork of Jbuilder, built of what they have accopmlished and with out Jbuilder TurboStreamer
would not be here today. Thanks to everyone who's been a part of Jbuilder!
-
David Heinemeier Hansson - david.heinemeierhansson.com/ - for writing Jbuidler!!
-
Pavel Pravosud - pavel.pravosud.com/ - for maintaing and pushing Jbuilder forward