Ruby Method Parameter Default Values – A Shortcut

Today was one of those moments where I thought to myself: “wouldn’t it be cool if I could”… and it turned out I could. In Ruby, you can give your method parameters default values:

def my_method(a = 5)
	puts a
end

my_method # outputs: 5

So far, so ordinary. But you can also do something a bit more interesting – populate your parameter defaults from instance variables:

class MyClass
	def initialize
		@default_a = 5
	end

	def my_method(a = @default_a)
		puts a
	end
end

MyClass.new.my_method # outputs: 5

There’s probably some Ruby gurus looking at this and thinking *OH MY GOD WHAT ARE YOU DOING* but in my case, it saved me having to create a method which “seeded” a second method with some default values; a few lines of code successfully saved.