Can anyone clearly explain to me all about ruby classes Especially using self.

This is going to be a case of the blind leading the blind, but no one else has answered in 2 weeks, so I'm going to give it a go since 'self' has been plaguing me too.

Warning! Most of this is stolen from other people and I understand it poorly.

definition: 'self' is the receiver object of the current method

For example:

array.size means array is the receiver object and size is the method.

Q1. So what is the self method?

self is not a method, it is the object a method is applied to

Q2. What does ruby mean by self is implied?

self is the implied receiver. The keyword self in Ruby gives you access to the current object – the object that is receiving the current message.

Q3. How does self work inside a method in a class?

In the context of a class, self refers to the current class. Inside of a class, self points to that class. This is critical to understanding self.

class Dog
  puts self # => Dog
end

Defining a method on self creates a class method vs. an instance method.

class MyClass
  def self.foo
    puts 'I am a class method'
  end

  def bar
    puts 'I am an instance method'
  end
end

MyClass.foo # => "I am a class method"
MyClass.new.bar # => "I am an instance method"

Another way of defining the same class method and instance method:

class MyClass
  class << self
    def foo
      puts 'I am still a class method'
    end
  end

  def bar
    puts 'I am still an instance method'
  end
end

MyClass.foo # => "I am still a class method"
MyClass.new.bar # => "I am still an instance method"

Classes group similar objects and describe Attributes and Behaviour. For example: in class Dog, all dogs have a name and breed; they can also bark. The attributes (or properties) are name and breed, the behaviour (or method) is bark. Here are some other resources: https://www.youtube.com/watch?v=SS-9y0H3Si8 http://www.codecademy.com/courses/ruby-beginner-en-MFiQ6/0/1

Q4. How does self work outside of a class?

Q5. How does self work with child classes?

I don't know the answers to this.

Perhaps Maciej Czuchnowski would correct any mistakes I have made and answer the rest of your questions?

Christine, I don't see any mistakes that would need a correction :)

To understand self, you have to read some explanations and examples given by various people and then experiment on your own in the interpreter. Some of my favorite explanations:

http://stackoverflow.com/a/6671310

http://www.jimmycuadra.com/posts/self-in-ruby

I still go through trial-and-error when dealing with self. It's not something I understand thoroughly and use everyday, but hopefully these links will help you :). And like I said, as with anything in programming, write some weird combinations of class methods, instance methods and local variables and run that code to see how it behaves.

Well, that's very affirming! I read both of those pages. Repeatedly. I stole from the first.

Karan, I also found two other links. The first is very quick and easy to go through and explains objects, classes and methods simply and clearly. The second has tons of self examples.

http://www.codequizzes.com/learn-ruby/intro-object-oriented-programming

http://www.eriktrautman.com/posts/ruby-explained-classes

Q4. How does self work outside of a class?

self is always defined. Try typing this in and out of irb: in irb self has many irb methods:

self.inspect # => "main"
self.class # => Object
self.methods.sort # (a  long list...)

You can use self inside of instance methods, (which inherit from the class Object); however, as you can see, the keyword self is not necessary - it is implicit (vs. explicit). Try running the same program, changing only line2:

def self.bark to def bark - self.bark still works.

def fido
  def self.bark
    "Arf!"
  end
  p self # => main
  p self.bark # => "Arf!"
end

p fido.bark # => "Arf!"

Q5. How does self work with child classes?

class Dog 
  def self.bark
    "Woof!"
  end
  p self # => Dog
end

class Snoopy < Dog
  def self.speak
    "<Silence>"
  end
  p self # => Snoopy
end

p Snoopy.bark # Woof!
p Snoopy.speak # <Silence>

There's more, but it involves singletons and the eigenclass and I've found it quite challenging. http://madebydna.com/all/code/2011/06/24/eigenclasses-demystified.html

Hey! Thanks, guys! I haven't been using tree house. Although I am relearning ruby with a different resource. I will be sure to update what my understanding of self is post that!