diff options
Diffstat (limited to 'actionview/lib/action_view/helpers/capture_helper.rb')
| -rw-r--r-- | actionview/lib/action_view/helpers/capture_helper.rb | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/actionview/lib/action_view/helpers/capture_helper.rb b/actionview/lib/action_view/helpers/capture_helper.rb new file mode 100644 index 0000000000..5afe435459 --- /dev/null +++ b/actionview/lib/action_view/helpers/capture_helper.rb @@ -0,0 +1,216 @@ +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 |