Editing Double dispatch (section)

===== SHAPE =====
The SHAPE class has the basis (e.g. drawing data) for what is drawn, perhaps on a SURFACE, but it does not have to be. Again, the agents provide the indirection and class agnostics required to make the co-variant relationship with SHAPE as decoupled as possible.

Additionally, please take note of the fact that SHAPE only provides `drawing_data_agent' as a fully exported feature to any client. Therefore, the only way to interact with SHAPE, other than creation, is through the facilities of the `drawing_data_agent', which is used by ANY client to indirectly and polymorphically gather drawing data for the SHAPE!

<syntaxhighlight lang="eiffel" line>
	deferred class
		SHAPE
	
	feature {NONE} -- Initialization
	
		make_with_color (a_color: like color)
				-- Make with `a_color' as `color'.
			do
				color := a_color
				drawing_data_agent := agent drawing_data
			ensure
				color_set: color.same_string (a_color)
			end

	feature -- Access
	
		drawing_data_agent: FUNCTION [ANY, TUPLE, like drawing_data]
				-- Data agent for drawing.
	
	feature {NONE} -- Implementation
	
		drawing_data: TUPLE [name: like name; color: like color]
				-- Data needed for drawing of Current.
			do
				Result := [name, color]
			end
	
		name: STRING
				-- Object name of Current.
			deferred end
	
		color: STRING
				-- Color of Current.

	end
</syntaxhighlight>