Ruby is Object Oriented

Answering to requests of our hundreds of readers :) I'm going to continue posting about Ruby language. So, today I'm going to say about object orientation in Ruby, specifically how to write a simple class, write methods (that's what I know to do with Ruby for the time being), etc.

So, below you can see a simple class written in Ruby:

class MyClass
end

And an object instantiation:

m = MyClass.new

Adding methods is very easy too:

class MyClass
   def my_method
      puts "That's a Ruby method!";
   end
end

If you're using irb (interactive ruby), a tool to execute interactively ruby expressions read from stdin, you don't have to re-instantiate 'm', the changes made in MyClass will affect 'm' dynamically (on the fly), so if you call 'm.my_method', don't worry, it'll work.

If you're not sure about a method in a object, you can do this:

if m.respond_to? "my_method"
   m.my_method
end

Do I need to explain something else?

The 'initialize' method represents a constructor in a Ruby class and the parameters come after:

class MyClass
   def initialize name = "Hello World!"
      @name = name
   end
   def hello
      puts "#{@name}"
   end
end

The '@name' is a field, like 'private Object obj;' in Java, and in the case above 'name' has "Hello World!" as its default value.

If you try to call 'm.name' you'll get something like:

NoMethodError: undefined method `name' for ...

This is because name is 'private', to create 'getters' and 'setters' you have to add 'attr_accessor :name' before the constructor. So, after that you can call 'm.name' or 'm.name = "hello"', for example, as you wish.