module ActionView
module Helpers
# Capture lets you extract parts of code 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
# make the fragment available by name to a yielding layout or template.
#
# 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">
# <%= yield :script %>
# </script>
# </head>
# <body>
# <%= yield %>
# </body>
# </html>
#
# view.rhtml
#
# This page shows an alert box!
#
# <% content_for("script") do %>
# alert('hello world')
# <% end %>
#
# Normal view text
module CaptureHelper
# 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 of capture being used in a .rhtml page:
#
# <% @greeting = capture do %>
# Welcome To my shiny new web page!
# <% end %>
#
# Example of capture being used in a .rxml page:
#
# @greeting = capture do
# 'Welcome To my shiny new web page!'
# end
def capture(*args, &block)
# execute the block
begin
buffer = eval(ActionView::Base.erb_variable, block.binding)
rescue
buffer = nil
end
if buffer.nil?
capture_block(*args, &block).to_s
else
capture_erb_with_buffer(buffer, *args, &block).to_s
end
end
# Calling content_for stores the block of markup for later use.
# Subsequently, you can make calls to it by name with <tt>yield</tt>
# in another template or in the layout.
#
# Example:
#
# <% content_for("header") do %>
# alert('hello world')
# <% end %>
#
# You can use yield :header anywhere in your templates.
#
# <%= yield :header %>
#
# NOTE: Beware that content_for is ignored in caches. So you shouldn't use it
# for elements that are going to be fragment cached.
#
# The deprecated way of accessing a content_for block was to use a instance variable
# named @@content_for_#{name_of_the_content_block}@. So <tt><%= content_for('footer') %></tt>
# would be avaiable as <tt><%= @content_for_footer %></tt>. The preferred notation now is
# <tt><%= yield :footer %></tt>.
def content_for(name, content = nil, &block)
eval "@content_for_#{name} = (@content_for_#{name} || '') + capture(&block)"
end
private
def capture_block(*args, &block)
block.call(*args)
end
def capture_erb(*args, &block)
buffer = eval(ActionView::Base.erb_variable, block.binding)
capture_erb_with_buffer(buffer, *args, &block)
end
def capture_erb_with_buffer(buffer, *args, &block)
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
def erb_content_for(name, &block)
eval "@content_for_#{name} = (@content_for_#{name} || '') + capture_erb(&block)"
end
def block_content_for(name, &block)
eval "@content_for_#{name} = (@content_for_#{name} || '') + capture_block(&block)"
end
end
end
end
