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module ActionView
module Helpers
# 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
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:
#
# <% @greeting = capture do %>
# Welcome To my shiny new web page!
# <% end %>
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 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.
def content_for(name, &block)
base = instance_variable_get(instance_var_name(name)) || ""
data = capture(&block)
instance_variable_set(instance_var_name(name), base + data)
data
end
private
def instance_var_name(name) #:nodoc#
"@content_for_#{name}"
end
end
end
end
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