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