function overloading

function_overloading.rb

#!/usr/bin/ruby

module FunctionOverloading
	def self.included(base)
		base.extend(ClassMethods)
		base.instance_variable_set(:@overloaded_methods, {})
	end
	
	module ClassMethods
		def method_added(name)
			super
			return if @adding_method
			method = instance_method(name)
			arity = method.arity
			
			@overloaded_methods[name] ||= {}
			if @overloaded_methods[name][arity]
				raise "Method '#{name}' with arity #{arity} already defined"
			end
			
			@overloaded_methods[name][arity] = method
			
			@adding_method = true
			define_method(name) do |*args|
				arity = args.size
				if method = self.class.instance_variable_get(:@overloaded_methods)[name][arity]
					method.bind(self).call(*args)
				else
					raise ArgumentError, "No method '#{name}' with arity #{arity}"
				end
			end
			@adding_method = false
		end
	end
end

# Usage
include FunctionOverloading

def my_method(x)
	"Called with one argument: #{x}"
end

def my_method(x, y)
	"Called with two arguments: #{x}, #{y}"
end

puts my_method(1)        # Output: Called with one argument: 1
puts my_method(1, 2)     # Output: Called with two arguments: 1, 2
# obj.my_method(1, 2, 3)     # Raises ArgumentError