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capturing.rb
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capturing.rb
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# encoding: utf-8
module Nanoc::Helpers
# 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>
#
# @example Showing captured content in a sidebar the old, deprecated way (do not use or I will become very angry)
#
# <div id="sidebar">
# <h3>Summary</h3>
# <%= @item[:content_for_summary] || '(no summary)' %>
# </div>
module Capturing
# @api private
class CapturesStore
def initialize
@store = {}
end
def []=(item, name, content)
@store[item.identifier] ||= {}
@store[item.identifier][name] = content
end
def [](item, name)
@store[item.identifier] ||= {}
@store[item.identifier][name]
end
end
class ::Nanoc::Site
# @api private
def captures_store
@captures_store ||= CapturesStore.new
end
end
# @overload content_for(name, &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.
#
# For backwards compatibility, it is also possible to fetch the captured
# content by getting the contents of the attribute named `content_for_`
# followed by the given name. This way of accessing captures is
# deprecated.
#
# @param [Symbol, String] name The base name of the attribute into which
# the content should be stored
#
# @return [void]
#
# @overload content_for(item, name)
#
# Fetches the capture with the given name from the given item and
# returns it.
#
# @param [Nanoc::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
def content_for(*args, &block)
if block_given? # Set content
# Get args
if args.size != 1
raise ArgumentError, "expected 1 argument (the name " +
"of the capture) but got #{args.size} instead"
end
name = args[0]
# Capture and store
content = capture(&block)
@site.captures_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]
name = args[1]
# Get content
@site.captures_store[item, name.to_sym]
end
end
# Evaluates the given block and returns its contents. The contents of the
# block is not outputted.
#
# @return [String] The captured result
def capture(&block)
# Get erbout so far
erbout = eval('_erbout', block.binding)
erbout_length = erbout.length
# Execute block
block.call
# Get new piece of erbout
erbout_addition = erbout[erbout_length..-1]
# Remove addition
erbout[erbout_length..-1] = ''
# Done
erbout_addition
end
end
end