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module ActionView::Helpers::RenderingHelper

Action View Rendering Helpers

Implements methods that allow rendering from a view context. In order to use this module, all you need is to implement view_renderer that returns an ActionView::Renderer object.

Public instance methods

_layout_for(*args, &block)

Overrides _layout_for in the context object so it supports the case a block is passed to a partial. Returns the contents that are yielded to a layout, given a name or a block.

You can think of a layout as a method that is called with a block. If the user calls yield :some_name, the block, by default, returns content_for(:some_name). If the user calls simply yield, the default block returns content_for(:layout).

The user can override this default by passing a block to the layout:

# 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:

# 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 render :layout, and the struct specified would be passed into the block as an argument. The result would be

<html>
  Hello David
</html>
Source code GitHub 
# File actionview/lib/action_view/helpers/rendering_helper.rb, line 97
def _layout_for(*args, &block)
  name = args.first

  if block && !name.is_a?(Symbol)
    capture(*args, &block)
  else
    super
  end
end

render(options = {}, locals = {}, &block)

Returns the result of a render that’s dictated by the options hash. The primary options are:

  • :partial - See ActionView::PartialRenderer.

  • :file - Renders an explicit template file (this used to be the old default), add :locals to pass in those.

  • :inline - Renders an inline template similar to how it’s done in the controller.

  • :plain - Renders the text passed in out. Setting the content type as text/plain.

  • :html - Renders the HTML safe string passed in out, otherwise performs HTML escape on the string first. Setting the content type as text/html.

  • :body - Renders the text passed in, and inherits the content type of text/plain from ActionDispatch::Response object.

If no options hash is passed or if :update is specified, then:

If an object responding to render_in is passed, render_in is called on the object, passing in the current view context.

Otherwise, a partial is rendered using the second parameter as the locals hash.

Source code GitHub 
# File actionview/lib/action_view/helpers/rendering_helper.rb, line 30
def render(options = {}, locals = {}, &block)
  case options
  when Hash
    in_rendering_context(options) do |renderer|
      if block_given?
        view_renderer.render_partial(self, options.merge(partial: options[:layout]), &block)
      else
        view_renderer.render(self, options)
      end
    end
  else
    if options.respond_to?(:render_in)
      options.render_in(self, &block)
    else
      view_renderer.render_partial(self, partial: options, locals: locals, &block)
    end
  end
end

Definition files