require 'active_support/core_ext/object/blank' 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. # # ==== Examples # 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: # # # <%= @greeting %> # # <%= @greeting %> # # def capture(*args) value = nil buffer = with_output_buffer { value = yield(*args) } if string = buffer.presence || value and string.is_a?(String) NonConcattingString.new(string) end end # Calling content_for stores a block of markup in an identifier for later use. # You can make subsequent calls to the stored content in other templates, helper modules # or the layout by passing the identifier as an argument to content_for. # # Note: yield can still be used to retrieve the stored content, but calling # yield doesn't work in helper modules, while content_for does. # # ==== Examples # # <% content_for :not_authorized do %> # alert('You are not authorized to do that!') # <% end %> # # You can then use content_for :not_authorized anywhere in your templates. # # <%= content_for :not_authorized if current_user.nil? %> # # This is equivalent to: # # <%= yield :not_authorized if current_user.nil? %> # # content_for, 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 use the yield syntax alongside an existing call to yield in a layout. For example: # # <%# This is the layout %> # # # My Website # <%= yield :script %> # # # <%= yield %> # # # # And now, we'll create a view that has a content_for call that # creates the script identifier. # # <%# This is our view %> # Please login! # # <% content_for :script do %> # # <% 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