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b00e6a984d
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7106 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
140 lines
4.8 KiB
Ruby
140 lines
4.8 KiB
Ruby
module ActionView
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module Helpers
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# CaptureHelper exposes methods to let you extract generated markup which
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# can be used in other parts of a template or layout file.
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# It provides a method to capture blocks into variables through capture and
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# a way to capture a block of code for use in a layout through content_for.
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module CaptureHelper
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# The capture method allows you to extract a part of the template into a
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# variable. You can then use this value anywhere in your templates or layout.
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#
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# ==== Examples
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# The capture method can be used in RHTML (ERb) templates...
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#
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# <% @greeting = capture do %>
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# Welcome to my shiny new web page! The date and time is
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# <%= Time.now %>
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# <% end %>
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#
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# ...and Builder (RXML) templates.
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#
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# @timestamp = capture do
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# "The current timestamp is #{Time.now}."
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# end
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#
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# You can then use the content as a variable anywhere else. For
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# example:
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#
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# <html>
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# <head><title><%= @greeting %></title></head>
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# <body>
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# <b><%= @greeting %></b>
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# </body></html>
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#
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def capture(*args, &block)
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# execute the block
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begin
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buffer = eval(ActionView::Base.erb_variable, block.binding)
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rescue
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buffer = nil
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end
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if buffer.nil?
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capture_block(*args, &block).to_s
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else
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capture_erb_with_buffer(buffer, *args, &block).to_s
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end
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end
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# Calling content_for stores the block of markup in an identifier for later use.
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# You can make subsequent calls to the stored content in another template or in the layout
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# by calling it by name with <tt>yield</tt>.
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#
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# ==== Examples
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#
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# <% content_for("authorized") do %>
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# alert('You are not authorized for that!')
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# <% end %>
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#
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# You can then use <tt>yield :authorized</tt> anywhere in your templates.
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#
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# <%= yield :authorized if current_user == nil %>
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#
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# You can also use these variables in a layout. For example:
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#
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# <!-- This is the layout -->
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# <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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# <head>
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# <title>My Website</title>
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# <%= yield :script %>
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# </head>
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# <body>
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# <%= yield %>
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# </body>
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# </html>
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#
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# And now we'll create a view that has a content_for call that
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# creates the <tt>script</tt> identifier.
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#
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# <!-- This is our view -->
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# Please login!
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#
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# <% content_for("script") do %>
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# <script type="text/javascript">alert('You are not authorized for this action!')</script>
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# <% end %>
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#
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# Then in another view you may want to do something like this:
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#
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# <%= link_to_remote 'Logout', :action => 'logout' %>
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#
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# <% content_for("script") do %>
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# <%= javascript_include_tag :defaults %>
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# <% end %>
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#
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# That will include Prototype and Scriptaculous into the page; this technique
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# is useful if you'll only be using these scripts on a few views.
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#
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# NOTE: Beware that content_for is ignored in caches. So you shouldn't use it
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# for elements that are going to be fragment cached.
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#
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# The deprecated way of accessing a content_for block was to use a instance variable
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# named @@content_for_#{name_of_the_content_block}@. So <tt><%= content_for('footer') %></tt>
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# would be avaiable as <tt><%= @content_for_footer %></tt>. The preferred notation now is
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# <tt><%= yield :footer %></tt>.
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def content_for(name, content = nil, &block)
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eval "@content_for_#{name} = (@content_for_#{name} || '') + capture(&block)"
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end
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private
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def capture_block(*args, &block)
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block.call(*args)
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end
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def capture_erb(*args, &block)
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buffer = eval(ActionView::Base.erb_variable, block.binding)
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capture_erb_with_buffer(buffer, *args, &block)
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end
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def capture_erb_with_buffer(buffer, *args, &block)
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pos = buffer.length
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block.call(*args)
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# extract the block
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data = buffer[pos..-1]
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# replace it in the original with empty string
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buffer[pos..-1] = ''
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data
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end
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def erb_content_for(name, &block)
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eval "@content_for_#{name} = (@content_for_#{name} || '') + capture_erb(&block)"
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end
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def block_content_for(name, &block)
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eval "@content_for_#{name} = (@content_for_#{name} || '') + capture_block(&block)"
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end
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end
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end
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end
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