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+require 'active_support/core_ext/string/output_safety'
+
+module ActionView
+ # = Action View Capture Helper
+ module Helpers
+ # CaptureHelper exposes methods to let you extract generated markup which
+ # can be used in other parts of a template or layout file.
+ #
+ # It provides a method to capture blocks into variables through capture and
+ # a way to capture a block of markup for use in a layout through content_for.
+ module CaptureHelper
+ # The capture method allows you to extract part of a template into a
+ # variable. You can then use this variable anywhere in your templates or layout.
+ #
+ # The capture method can be used in ERB templates...
+ #
+ # <% @greeting = capture do %>
+ # Welcome to my shiny new web page! The date and time is
+ # <%= Time.now %>
+ # <% end %>
+ #
+ # ...and Builder (RXML) templates.
+ #
+ # @timestamp = capture do
+ # "The current timestamp is #{Time.now}."
+ # end
+ #
+ # You can then use that variable anywhere else. For example:
+ #
+ # <html>
+ # <head><title><%= @greeting %></title></head>
+ # <body>
+ # <b><%= @greeting %></b>
+ # </body></html>
+ #
+ def capture(*args)
+ value = nil
+ buffer = with_output_buffer { value = yield(*args) }
+ if string = buffer.presence || value and string.is_a?(String)
+ ERB::Util.html_escape string
+ end
+ end
+
+ # Calling content_for stores a block of markup in an identifier for later use.
+ # In order to access this stored content in other templates, helper modules
+ # or the layout, you would pass the identifier as an argument to <tt>content_for</tt>.
+ #
+ # Note: <tt>yield</tt> can still be used to retrieve the stored content, but calling
+ # <tt>yield</tt> doesn't work in helper modules, while <tt>content_for</tt> does.
+ #
+ # <% content_for :not_authorized do %>
+ # alert('You are not authorized to do that!')
+ # <% end %>
+ #
+ # You can then use <tt>content_for :not_authorized</tt> anywhere in your templates.
+ #
+ # <%= content_for :not_authorized if current_user.nil? %>
+ #
+ # This is equivalent to:
+ #
+ # <%= yield :not_authorized if current_user.nil? %>
+ #
+ # <tt>content_for</tt>, however, can also be used in helper modules.
+ #
+ # module StorageHelper
+ # def stored_content
+ # content_for(:storage) || "Your storage is empty"
+ # end
+ # end
+ #
+ # This helper works just like normal helpers.
+ #
+ # <%= stored_content %>
+ #
+ # You can also use the <tt>yield</tt> syntax alongside an existing call to
+ # <tt>yield</tt> in a layout. For example:
+ #
+ # <%# This is the layout %>
+ # <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
+ # <head>
+ # <title>My Website</title>
+ # <%= yield :script %>
+ # </head>
+ # <body>
+ # <%= yield %>
+ # </body>
+ # </html>
+ #
+ # And now, we'll create a view that has a <tt>content_for</tt> call that
+ # creates the <tt>script</tt> identifier.
+ #
+ # <%# This is our view %>
+ # Please login!
+ #
+ # <% content_for :script do %>
+ # <script>alert('You are not authorized to view this page!')</script>
+ # <% end %>
+ #
+ # Then, in another view, you could to do something like this:
+ #
+ # <%= link_to 'Logout', action: 'logout', remote: true %>
+ #
+ # <% content_for :script do %>
+ # <%= javascript_include_tag :defaults %>
+ # <% end %>
+ #
+ # That will place +script+ tags for your default set of JavaScript files on the page;
+ # this technique is useful if you'll only be using these scripts in a few views.
+ #
+ # Note that content_for concatenates (default) the blocks it is given for a particular
+ # identifier in order. For example:
+ #
+ # <% content_for :navigation do %>
+ # <li><%= link_to 'Home', action: 'index' %></li>
+ # <% end %>
+ #
+ # And in other place:
+ #
+ # <% content_for :navigation do %>
+ # <li><%= link_to 'Login', action: 'login' %></li>
+ # <% end %>
+ #
+ # Then, in another template or layout, this code would render both links in order:
+ #
+ # <ul><%= content_for :navigation %></ul>
+ #
+ # If the flush parameter is true content_for replaces the blocks it is given. For example:
+ #
+ # <% content_for :navigation do %>
+ # <li><%= link_to 'Home', action: 'index' %></li>
+ # <% end %>
+ #
+ # <%# Add some other content, or use a different template: %>
+ #
+ # <% content_for :navigation, flush: true do %>
+ # <li><%= link_to 'Login', action: 'login' %></li>
+ # <% end %>
+ #
+ # Then, in another template or layout, this code would render only the last link:
+ #
+ # <ul><%= content_for :navigation %></ul>
+ #
+ # Lastly, simple content can be passed as a parameter:
+ #
+ # <% content_for :script, javascript_include_tag(:defaults) %>
+ #
+ # WARNING: content_for is ignored in caches. So you shouldn't use it for elements that will be fragment cached.
+ def content_for(name, content = nil, options = {}, &block)
+ if content || block_given?
+ if block_given?
+ options = content if content
+ content = capture(&block)
+ end
+ if content
+ options[:flush] ? @view_flow.set(name, content) : @view_flow.append(name, content)
+ end
+ nil
+ else
+ @view_flow.get(name).presence
+ end
+ end
+
+ # The same as +content_for+ but when used with streaming flushes
+ # straight back to the layout. In other words, if you want to
+ # concatenate several times to the same buffer when rendering a given
+ # template, you should use +content_for+, if not, use +provide+ to tell
+ # the layout to stop looking for more contents.
+ def provide(name, content = nil, &block)
+ content = capture(&block) if block_given?
+ result = @view_flow.append!(name, content) if content
+ result unless content
+ end
+
+ # content_for? checks whether any content has been captured yet using `content_for`.
+ # Useful to render parts of your layout differently based on what is in your views.
+ #
+ # <%# This is the layout %>
+ # <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
+ # <head>
+ # <title>My Website</title>
+ # <%= yield :script %>
+ # </head>
+ # <body class="<%= content_for?(:right_col) ? 'two-column' : 'one-column' %>">
+ # <%= yield %>
+ # <%= yield :right_col %>
+ # </body>
+ # </html>
+ def content_for?(name)
+ @view_flow.get(name).present?
+ end
+
+ # Use an alternate output buffer for the duration of the block.
+ # Defaults to a new empty string.
+ def with_output_buffer(buf = nil) #:nodoc:
+ unless buf
+ buf = ActionView::OutputBuffer.new
+ buf.force_encoding(output_buffer.encoding) if output_buffer
+ end
+ self.output_buffer, old_buffer = buf, output_buffer
+ yield
+ output_buffer
+ ensure
+ self.output_buffer = old_buffer
+ end
+
+ # Add the output buffer to the response body and start a new one.
+ def flush_output_buffer #:nodoc:
+ if output_buffer && !output_buffer.empty?
+ response.stream.write output_buffer
+ self.output_buffer = output_buffer.respond_to?(:clone_empty) ? output_buffer.clone_empty : output_buffer[0, 0]
+ nil
+ end
+ end
+ end
+ end
+end