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path: root/actionpack/lib/action_view/render/rendering.rb
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require 'active_support/core_ext/object/try'

module ActionView
  module Rendering
    # Returns the result of a render that's dictated by the options hash. The primary options are:
    #
    # * <tt>:partial</tt> - See ActionView::Partials.
    # * <tt>:update</tt> - Calls update_page with the block given.
    # * <tt>:file</tt> - Renders an explicit template file (this used to be the old default), add :locals to pass in those.
    # * <tt>:inline</tt> - Renders an inline template similar to how it's done in the controller.
    # * <tt>:text</tt> - Renders the text passed in out.
    #
    # If no options hash is passed or :update specified, the default is to render a partial and use the second parameter
    # as the locals hash.
    def render(options = {}, locals = {}, &block) #:nodoc:
      case options
      when Hash
        layout = options[:layout]
        options[:locals] ||= {}

        if block_given?
          return concat(_render_partial(options.merge(:partial => layout), &block))
        elsif options.key?(:partial)
          return _render_partial(options)
        end

        template = if options[:file]
          find(options[:file], {:formats => formats})
        elsif options[:inline]
          handler = Template.handler_class_for_extension(options[:type] || "erb")
          Template.new(options[:inline], "inline template", handler, {})
        elsif options[:text]
          Template::Text.new(options[:text])
        end

        if template
          layout = find(layout, {:formats => formats}) if layout
          _render_template(template, layout, :locals => options[:locals])
        end
      when :update
        update_page(&block)
      else
        _render_partial(:partial => options, :locals => locals)
      end
    end

    # You can think of a layout as a method that is called with a block. _layout_for
    # returns the contents that are yielded to the layout. If the user calls yield
    # :some_name, the block, by default, returns content_for(:some_name). If the user
    # calls yield, the default block returns content_for(:layout).
    #
    # The user can override this default by passing a block to the layout.
    #
    # ==== Example
    #
    #   # The template
    #   <% render :layout => "my_layout" do %>Content<% end %>
    #
    #   # The layout
    #   <html><% yield %></html>
    #
    # In this case, instead of the default block, which would return content_for(:layout),
    # this method returns the block that was passed in to render layout, and the response
    # would be <html>Content</html>.
    #
    # Finally, the block can take block arguments, which can be passed in by yield.
    #
    # ==== Example
    #
    #   # The template
    #   <% render :layout => "my_layout" do |customer| %>Hello <%= customer.name %><% end %>
    #
    #   # The layout
    #   <html><% yield Struct.new(:name).new("David") %></html>
    #
    # In this case, the layout would receive the block passed into <tt>render :layout</tt>,
    # and the Struct specified in the layout would be passed into the block. The result
    # would be <html>Hello David</html>.
    def _layout_for(name = nil, &block)
      return @_content_for[name || :layout] if !block_given? || name
      capture(&block)
    end

    # This is the API to render a ViewContext's template from a controller.
    #
    # Internal Options:
    # _template:: The Template object to render
    # _layout::   The layout, if any, to wrap the Template in
    def render_template(options)
      _evaluate_assigns_and_ivars
      template, layout = options.values_at(:_template, :_layout)
      _render_template(template, layout, options)
    end

    def _render_template(template, layout = nil, options = {})
      locals = options[:locals] || {}

      ActiveSupport::Notifications.instrument("action_view.render_template",
        :identifier => template.identifier, :layout => layout.try(:identifier)) do

        content = template.render(self, locals)
        @_content_for[:layout] = content

        if layout
          @_layout = layout.identifier
          content  = _render_layout(layout, locals)
        end

        content
      end
    end

    def _render_layout(layout, locals, &block)
      layout.render(self, locals){ |*name| _layout_for(*name, &block) }
    end
  end
end