Module: ActionView::Helpers::CaptureHelper

Defined in:
lib/action_view/helpers/capture_helper.rb

Overview

Capture lets you extract parts of code into instance variables which can be used in other points of the template or even layout file.

Capturing a block into an instance variable

<% @script = capture do %>
  [some html...]
<% end %>

Add javascript to header using content_for

content_for(“name”) is a wrapper for capture which will store the fragment in a instance variable similar to @content_for_layout.

layout.rhtml:

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
  <title>layout with js</title>
  <script type="text/javascript">
  <%= @content_for_script %>
	</script>
</head>
<body>
  <%= @content_for_layout %>
</body>
</html>

view.rhtml

This page shows an alert box!

<% content_for("script") do %>
  alert('hello world')
<% end %>

Normal view text

Instance Method Summary collapse

Instance Method Details

#capture(*args, &block) ⇒ Object

Capture allows you to extract a part of the template into an instance variable. You can use this instance variable anywhere in your templates and even in your layout.

Example:

<% @greeting = capture do %>
  Welcome To my shiny new web page!
<% end %>

51
52
53
54
55
56
57
58
59
60
61
62
63
64
# File 'lib/action_view/helpers/capture_helper.rb', line 51

def capture(*args, &block)
  # execute the block
  buffer = eval("_erbout", block.binding)
  pos = buffer.length
  block.call(*args)
  
  # extract the block 
  data = buffer[pos..-1]
  
  # replace it in the original with empty string
  buffer[pos..-1] = ''
  
  data
end

#content_for(name, &block) ⇒ Object

Content_for will store the given block in an instance variable for later use in another template or in the layout.

The name of the instance variable is content_for_<name> to stay consistent with @content_for_layout which is used by ActionView's layouts

Example:

<% content_for("header") do %>
  alert('hello world')
<% end %>

You can use @content_for_header anywhere in your templates.

NOTE: Beware that content_for is ignored in caches. So you shouldn't use it for elements that are going to be fragment cached.


84
85
86
# File 'lib/action_view/helpers/capture_helper.rb', line 84

def content_for(name, &block)
  eval "@content_for_#{name} = (@content_for_#{name} || '') + capture(&block)"
end