class Chef::Resource::Template
A cookbook template is an Embedded Ruby
(ERB) template that is used to dynamically generate static text files. Templates may contain Ruby
expressions and statements, and are a great way to manage configuration files. Use the template resource to add cookbook templates to recipes; place the corresponding Embedded Ruby
(ERB) template file in a cookbook’s /templates directory.
Use the template resource to manage the contents of a file using an Embedded Ruby
(ERB) template by transferring files from a sub-directory of COOKBOOK_NAME/templates/ to a specified path located on a host that is running the chef-client. This resource includes actions and properties from the file resource. Template
files managed by the template resource follow the same file specificity rules as the remote_file and file resources.
Attributes
Public Class Methods
Source
# File lib/chef/resource/template.rb, line 45 def initialize(name, run_context = nil) super @source = "#{::File.basename(name)}.erb" @inline_helper_blocks = {} @inline_helper_modules = [] @helper_modules = [] end
Chef::Resource::new
Public Instance Methods
Source
# File lib/chef/resource/template.rb, line 106 def helper(method_name, &block) unless block_given? raise Exceptions::ValidationFailed, "`helper(:method)` requires a block argument (e.g., `helper(:method) { code }`)" end unless method_name.is_a?(Symbol) raise Exceptions::ValidationFailed, "method_name argument to `helper(method_name)` must be a symbol (e.g., `helper(:method) { code }`)" end @inline_helper_blocks[method_name] = block end
Declares a helper method to be defined in the template context when rendering.
Example:¶ ↑
Basic usage:¶ ↑
Given the following helper:
helper(:static_value) { "hello from helper" }
A template with the following code:
<%= static_value %>
Will render as;
hello from helper
Referencing Instance Variables:¶ ↑
Any instance variables available to the template can be referenced in the method body. For example, you can simplify accessing app-specific node attributes like this:
helper(:app) { @node[:my_app_attributes] }
And use it in a template like this:
<%= app[:listen_ports] %>
This is equivalent to the non-helper template code:
<%= @node[:my_app_attributes][:listen_ports] %>
Method Arguments:¶ ↑
Helper methods can also take arguments. The syntax available for argument specification supports full syntax available for method definition.
Continuing the above example of simplifying attribute access, we can define a helper to look up app-specific attributes like this:
helper(:app) { |setting| @node[:my_app_attributes][setting] }
The template can then look up attributes like this:
<%= app(:listen_ports) %>
Source
# File lib/chef/resource/template.rb, line 183 def helper_modules compiled_helper_methods + compiled_helper_modules + @helper_modules end
Compiles all helpers from inline method definitions, inline module definitions, and external modules into an Array of Modules. The context object for the template is extended with these modules to provide per-resource template logic.
Source
# File lib/chef/resource/template.rb, line 160 def helpers(module_name = nil, &block) if block_given? && !module_name.nil? raise Exceptions::ValidationFailed, "Passing both a module and block to #helpers is not supported. Call #helpers multiple times instead" elsif block_given? @inline_helper_modules << block elsif module_name.is_a?(::Module) @helper_modules << module_name elsif module_name.nil? raise Exceptions::ValidationFailed, "#helpers requires either a module name or inline module code as a block.\n" + "e.g.: helpers do; helper_code; end;\n" + "OR: helpers(MyHelpersModule)" else raise Exceptions::ValidationFailed, "Argument to #helpers must be a module. You gave #{module_name.inspect} (#{module_name.class})" end end
Declares a module to define helper methods in the template’s context when rendering. There are two primary forms.
Inline Module Definition¶ ↑
When a block is given, the block is used to define a module which is then mixed in to the template context w/ ‘extend`.
Inline Module Example¶ ↑
Given the following code in the template resource:
helpers do # Add "syntax sugar" for referencing app-specific attributes def app(attribute) @node[:my_app_attributes][attribute] end end
You can use it in the template like so:
<%= app(:listen_ports) %>
Which is equivalent to:
<%= @node[:my_app_attributes][:listen_ports] %>
External Module Form¶ ↑
When a module name is given, the template context will be extended with that module. This is the recommended way to customize template contexts when you need to define more than an handful of helper functions (but also try to keep your template helpers from getting out of hand–if you have very complex logic in your template helpers, you should further extract your code into separate libraries).
External Module Example¶ ↑
To extract the above inline module code to a library, you’d create a library file like this:
module MyTemplateHelper # Add "syntax sugar" for referencing app-specific attributes def app(attribute) @node[:my_app_attributes][attribute] end end
And in the template resource:
helpers(MyTemplateHelper)
The template code in the above example will work unmodified.
Source
# File lib/chef/resource/template.rb, line 53 def source(file = nil) set_or_return( :source, file, kind_of: [ String, Array ] ) end
Private Instance Methods
Source
# File lib/chef/resource/template.rb, line 190 def compiled_helper_methods if inline_helper_blocks.empty? [] else resource_helper_blocks = inline_helper_blocks helper_mod = Module.new do resource_helper_blocks.each do |method_name, method_body| define_method(method_name, &method_body) end end [ helper_mod ] end end
compiles helper methods into a module that can be included in template context
Source
# File lib/chef/resource/template.rb, line 204 def compiled_helper_modules @inline_helper_modules.map do |module_body| Module.new(&module_body) end end