Question

I come from Java and am wondering if interfaces exist in ruby? how can you mimic a contractual behavior that a Java interface provides?

For example:

interface ContactService {
    public boolean successful(Contract contract);
}

Answer 1

There is no real concept of an interface in Ruby. Instead, people tend to just write general methods that don’t care about the type of the objects they are operating on, and just use some specific set of methods that the object will need to implement.

For example:

def add(a,b)
  a+b
end

The add method doesn’t care if its arguments are integers, strings, or arrays. They just have to be some object that implements the + operator.

def calltwice(obj)
  obj.call
  obj.call
end

The calltwice method doesn’t care if obj is a lambda, proc, or some custom class. It just cares that the object has a call method.

You can informally define an interface in the comments by telling the users of your code what methods will be called an how they should behave.