162 lines
5.6 KiB
Ruby
162 lines
5.6 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 markup 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 part of a template into a
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# variable. You can then use this variable 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 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 that variable anywhere else. For 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 a block of markup in an identifier for later use.
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# You can make subsequent calls to the stored content in other templates or the layout
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# by passing the identifier as an argument to <tt>yield</tt>.
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#
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# ==== Examples
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#
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# <% content_for :not_authorized do %>
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# alert('You are not authorized to do that!')
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# <% end %>
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#
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# You can then use <tt>yield :not_authorized</tt> anywhere in your templates.
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#
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# <%= yield :not_authorized if current_user.nil? %>
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#
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# You can also use this syntax alongside an existing call to <tt>yield</tt> 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 to view this page!')</script>
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# <% end %>
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#
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# Then, in another view, you could 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 place <script> tags for Prototype, Scriptaculous, and application.js (if it exists)
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# on the page; this technique is useful if you'll only be using these scripts in a few views.
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#
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# Note that content_for concatenates the blocks it is given for a particular
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# identifier in order. For example:
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#
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# <% content_for :navigation do %>
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# <li><%= link_to 'Home', :action => 'index' %></li>
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# <% end %>
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#
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# <%# Add some other content, or use a different template: %>
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#
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# <% content_for :navigation do %>
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# <li><%= link_to 'Login', :action => 'login' %></li>
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# <% end %>
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#
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# Then, in another template or layout, this code would render both links in order:
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#
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# <ul><%= yield :navigation %></ul>
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#
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# Lastly, simple content can be passed as a parameter:
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#
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# <% content_for :script, javascript_include_tag(:defaults) %>
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#
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# WARNING: content_for is ignored in caches. So you shouldn't use it
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# for elements that will be fragment cached.
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#
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# The deprecated way of accessing a content_for block is to use an instance variable
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# named <tt>@content_for_#{name_of_the_content_block}</tt>. The preferred usage is now
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# <tt><%= yield :footer %></tt>.
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def content_for(name, content = nil, &block)
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existing_content_for = instance_variable_get("@content_for_#{name}").to_s
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new_content_for = existing_content_for + (block_given? ? capture(&block) : content)
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instance_variable_set("@content_for_#{name}", new_content_for)
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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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