How to pass objects to the class method

Question

I have the following class method that uses default classes if no provided:

def self.make_sandwich(bread = Bread, butter = Butter, cheese = Cheese)
  ...
end

So I can call it and pass a new class of bread called MyBread

[class].make_sandwich(MyBread)

But how can I pass a bread and cheese without butter? I know I could change the order or use the attr_accessor to use the default class if no provided, but assume I cant modify that code that way

Answer 1

If you're on ruby 2.0 you can use keyword arguments.

If you're on older ruby, you can use hash opts parameter.

def self.make_sandwich(opts = {:bread => Bread, 
                               :butter => Butter, 
                               :cheese => Cheese})

  bread_to_use = opts[:bread]
end

make_sandwich(:bread => some_bread,
              :cheese => some_cheese)

Alternatively, you can set default values in the method's body and then just pass nil in the method call.

def self.make_sandwich(bread = nil, butter = nil, cheese = nil)
  bread ||= Bread
  butter ||= Butter
  cheese ||= Cheese
  ...
end

make_sandwich(bread, nil, cheese)