Module: Sinatra::ContentFor

Includes:
Capture
Defined in:
lib/sinatra/content_for.rb

Overview

Sinatra::ContentFor

Sinatra::ContentFor is a set of helpers that allows you to capture blocks inside views to be rendered later during the request. The most common use is to populate different parts of your layout from your view.

The currently supported engines are: Erb, Erubi, Haml and Slim.

Usage

You call content_for, generally from a view, to capture a block of markup giving it an identifier:

# index.erb
<% content_for :some_key do %>
  <chunk of="html">...</chunk>
<% end %>

Then, you call yield_content with that identifier, generally from a layout, to render the captured block:

# layout.erb
<%= yield_content :some_key %>

If you have provided yield_content with a block and no content for the specified key is found, it will render the results of the block provided to yield_content.

# layout.erb
<% yield_content :some_key_with_no_content do %>
  <chunk of="default html">...</chunk>
<% end %>

Classic Application

To use the helpers in a classic application all you need to do is require them:

require "sinatra"
require "sinatra/content_for"

# Your classic application code goes here...

Modular Application

To use the helpers in a modular application you need to require them, and then, tell the application you will use them:

require "sinatra/base"
require "sinatra/content_for"

class MyApp < Sinatra::Base
  helpers Sinatra::ContentFor

  # The rest of your modular application code goes here...
end

And How Is This Useful?

For example, some of your views might need a few javascript tags and stylesheets, but you don’t want to force this files in all your pages. Then you can put <%= yield_content :scripts_and_styles %> on your layout, inside the <head> tag, and each view can call content_for setting the appropriate set of tags that should be added to the layout.

Limitations

Due to the rendering process limitation using <%= yield_content %> from within nested templates do not work above the <tt><%= yield %> statement. For more details github.com/sinatra/sinatra-contrib/issues/140#issuecomment-48831668

# app.rb
get '/' do
  erb :body, :layout => :layout do
    erb :foobar
  end
end

# foobar.erb
<% content_for :one do %>
  <script>
    alert('one');
  </script>
<% end %>
<% content_for :two do %>
  <script>
    alert('two');
  </script>
<% end %>

Using <%= yield_content %> before <%= yield %> will cause only the second alert to display:

# body.erb
# Display only second alert
<%= yield_content :one %>
<%= yield %>
<%= yield_content :two %>

# body.erb
# Display both alerts
<%= yield %>
<%= yield_content :one %>
<%= yield_content :two %>

Instance Attribute Summary

Attributes included from EngineTracking

#current_engine

Instance Method Summary collapse

Methods included from Capture

#capture, #capture_later

Methods included from EngineTracking

#builder?, #erb?, #erubi?, #haml?, #initialize, #liquid?, #markaby?, #markdown?, #nokogiri?, #rdoc?, #ruby?, #sass?, #scss?, #slim?, #with_engine

Instance Method Details

#clear_content_for(key) ⇒ Object

Unset a named block of content. For example:

<% clear_content_for :head %>



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# File 'lib/sinatra/content_for.rb', line 155

def clear_content_for(key)
  content_blocks.delete(key.to_sym) if content_for?(key)
end

#content_for(key, value = nil, options = {}, &block) ⇒ Object

Capture a block of content to be rendered later. For example:

<% content_for :head do %>
  <script type="text/javascript" src="/foo.js"></script>
<% end %>

You can also pass an immediate value instead of a block:

<% content_for :title, "foo" %>

You can call content_for multiple times with the same key (in the example :head), and when you render the blocks for that key all of them will be rendered, in the same order you captured them.

Your blocks can also receive values, which are passed to them by yield_content



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# File 'lib/sinatra/content_for.rb', line 132

def content_for(key, value = nil, options = {}, &block)
  block ||= proc { |*| value }
  clear_content_for(key) if options[:flush]
  content_blocks[key.to_sym] << capture_later(&block)
end

#content_for?(key) ⇒ Boolean

Check if a block of content with the given key was defined. For example:

<% content_for :head do %>
  <script type="text/javascript" src="/foo.js"></script>
<% end %>

<% if content_for? :head %>
  <span>content "head" was defined.</span>
<% end %>

Returns:

  • (Boolean) 


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# File 'lib/sinatra/content_for.rb', line 148

def content_for?(key)
  content_blocks[key.to_sym].any?
end

#yield_content(key, *args, &block) ⇒ Object

Render the captured blocks for a given key. For example:

<head>
  <title>Example</title>
  <%= yield_content :head %>
</head>

Would render everything you declared with content_for :head before closing the <head> tag.

You can also pass values to the content blocks by passing them as arguments after the key:

<%= yield_content :head, 1, 2 %>

Would pass 1 and 2 to all the blocks registered for :head.



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# File 'lib/sinatra/content_for.rb', line 176

def yield_content(key, *args, &block)
  if block_given? && !content_for?(key)
    haml? && Tilt[:haml] == Tilt::HamlTemplate && respond_to?(:capture_haml) ? capture_haml(*args, &block) : yield(*args)
  else
    content = content_blocks[key.to_sym].map { |b| capture(*args, &b) }
    content.join.tap do |c|
      if block_given? && (erb? || erubi?)
        @_out_buf << c
      end
    end
  end
end