module Nanoc::Helpers::Capturing
Provides functionality for “capturing” content in one place and reusing this content elsewhere.
For example, suppose you want the sidebar of your site to contain a short summary of the item. You could put the summary in the meta file, but that’s not possible when the summary contains eRuby. You could also put the sidebar inside the actual item, but that’s not very pretty. Instead, you write the summary on the item itself, but capture it, and print it in the sidebar layout.
This helper has been tested with ERB and Haml. Other filters may not work correctly.
@example Capturing content for a summary
<% content_for :summary do %> <p>On this item, Nanoc is introduced, blah blah.</p> <% end %>
@example Showing captured content in a sidebar
<div id="sidebar"> <h3>Summary</h3> <%= content_for(@item, :summary) || '(no summary)' %> </div>
Public Instance Methods
Evaluates the given block and returns its contents. The contents of the block is not outputted.
@return [String] The captured result
# File lib/nanoc/helpers/capturing.rb, line 174 def capture(&block) # Get erbout so far erbout = eval('_erbout', block.binding) erbout_length = erbout.length # Execute block yield # Get new piece of erbout erbout_addition = erbout[erbout_length..-1] # Remove addition erbout[erbout_length..-1] = '' # Depending on how the filter outputs, the result might be a # single string or an array of strings (slim outputs the latter). erbout_addition = erbout_addition.join if erbout_addition.is_a? Array # Done. erbout_addition end
@overload #content_for(name, params = {}, &block)
Captures the content inside the block and stores it so that it can be referenced later on. The same method, {#content_for}, is used for getting the captured content as well as setting it. When capturing, the content of the block itself will not be outputted. By default, capturing content with the same name will raise an error if the newly captured content differs from the previously captured content. This behavior can be changed by providing a different `:existing` option to this method: * `:error`: When content already exists and is not identical, raise an error. * `:overwrite`: Overwrite the previously captured content with the newly captured content. * `:append`: Append the newly captured content to the previously captured content. @param [Symbol, String] name The base name of the attribute into which the content should be stored @option params [Symbol] existing Can be either `:error`, `:overwrite`, or `:append` @return [void]
@overload #content_for(item, name)
Fetches the capture with the given name from the given item and returns it. @param [Nanoc::Int::Item] item The item for which to get the capture @param [Symbol, String] name The name of the capture to fetch @return [String] The stored captured content
# File lib/nanoc/helpers/capturing.rb, line 96 def content_for(*args, &block) if block_given? # Set content # Get args case args.size when 1 name = args[0] params = {} when 2 name = args[0] params = args[1] else raise ArgumentError, 'expected 1 or 2 argument (the name ' "of the capture, and optionally params) but got #{args.size} instead" end name = args[0] existing_behavior = params.fetch(:existing, :error) # Capture content = capture(&block) # Prepare for store store = @site.unwrap.captures_store case existing_behavior when :overwrite store[@item, name.to_sym] = '' when :append store[@item, name.to_sym] ||= '' when :error if store[@item, name.to_sym] && store[@item, name.to_sym] != content raise "a capture named #{name.inspect} for #{@item.identifier} already exists" else store[@item, name.to_sym] = '' end else raise ArgumentError, 'expected :existing_behavior param to #content_for to be one of ' ":overwrite, :append, or :error, but #{existing_behavior.inspect} was given" end # Store @site.unwrap.captures_store_compiled_items << @item.unwrap store[@item, name.to_sym] << content else # Get content # Get args if args.size != 2 raise ArgumentError, 'expected 2 arguments (the item ' "and the name of the capture) but got #{args.size} instead" end item = args[0].is_a?(Nanoc::ItemWithRepsView) ? args[0].unwrap : args[0] name = args[1] # Create dependency if @item.nil? || item != @item.unwrap Nanoc::Int::NotificationCenter.post(:visit_started, item) Nanoc::Int::NotificationCenter.post(:visit_ended, item) # This is an extremely ugly hack to get the compiler to recompile the # item from which we use content. For this, we need to manually edit # the content attribute to reset it. :( # FIXME: clean this up unless @site.unwrap.captures_store_compiled_items.include?(item) @site.unwrap.captures_store.reset_for(item) item.forced_outdated = true @site.unwrap.compiler.reps[item].each do |r| r.snapshot_contents = { last: item.content } raise Nanoc::Int::Errors::UnmetDependency.new(r) end end end # Get content @site.unwrap.captures_store[item, name.to_sym] end end