Interfaces and Type Hinting?

[matsko]

I'm just starting out with Ruby and I've got a question about the OO features of the language.

Does Ruby support native interfaces, or do you need to code your own base or mixin setup?

And if you do manage to create a interface then is it possible to setup a type hint within a the parameters of a function to only allow a specific type of Class or Interface to be accepted?

sub someFunc(Class a)

end

Is this possible?

[ReggieB]

Does Ruby support native interfaces, or do you need to code your own base or mixin setup?

I think your question relates to inheritance. You can create a new class based on an existing class very easily in Ruby. You can also mixin other code using modules

class Animal
  def breath
    puts "Puff, puff"
  end
end

module FourLeggedAnimals
  def legs
    puts "4"
  end
end

class Dog < Animal
  include FourLeggedAnimals
  def bark
    puts "Woof, woof"
  end
end

dog = Dog.new
dog.breath   --->  "Puff, puff"
dog.bark     --->   "Woof, woof"
dog.legs      --->   "4"

And if you do manage to create a interface then is it possible to setup a type hint within a the parameters of a function to only allow a specific type of Class or Interface to be accepted?

Ruby is not strongly typed so no you cannot specify the type of input into a method in the way you suggest. However, you can determine the type of object passed in within the code and alter the behaviour to suit:

def get_something(something)
  # version that will only find Dogs
  if something.class == Dog
    # do dog only things
  elsif something.kind_of? Animal
    # do animal things
  else
    raise "Item is not an animal"
  end
end

Note that kind_of? will return true for objects that inherit from the class. So:

dog = Dog.new
dog.class == Animal    ---> false
dog.kind_of? Animal    ---> true

See the Object api for more details of class and kind_of? methods:

http://www.ruby-doc.org/core/classes/Object.html

[oddz]

I believe the answer to your question is duck typing.

[kyberfabrikken]

Ruby is not strongly typed so no you cannot specify the type of input into a method in the way you suggest.

Actually, Ruby is strongly typed. It's not statically typed however. And indeed, there is no way to enforce the type of a parameter in Ruby. The only way to get explicit interfaces in Ruby, is by documenting them. You can't have the runtime enforce it.