Basic Ruby — Class

Alright class. Who knows the definition for the word class?

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One of the english definition of class.

noun

noun: class; plural noun: classes

1.
a set or category of things having some property or attribute in common and differentiated from others by kind, type, or quality.

Ruby’s definition of what is a class?

A class is a blueprint from which objects are created. The object is also called as an instance of a class. For Example, the animal is a class and mammals, birds, fish, reptiles, and amphibians are the instances of the class. Similarly, the sales department is the class and the objects of the class are sales data, sales manager, and secretary.

Ruby is a true object-oriented programming language. Everything in ruby is an object. All objects contain data, attributes, properties and methods.

How to create a class? Thats easy. Just write the keyword class. Followed by a capitalized Name, that we want to give it. Also it has to be singular.

 class Cat
 end

That was it, we had created a new class of Cat. So what now?

Everything we call Cat.new, we create a new cat object or an instance from the Cat class factory. Each cat instance is different from one another. No two instances are the same. By adding methods to a class, we are providing addition attributes/information to the Cat class.

class Cat
    attr_accessor :name
   def initialize (name)
        @name = name
   end
   def sound
       puts "meow"
   end
   def jump
      skill = "jump"
      puts "the cat learned how to #{skill}."
   end
   def sleep
      puts "ZZZzzz"
   end
end 

We now given the Cat class 4 new methods + 2 methods from the macro, the attr_accessor, which is made up of attr_writer and attr_reader. Now every time we create a new cat instance, it will have a name, can be renamed, able to meow, able to learn how to jump and knows how to sleep.

The initialize method is a special method that it will call itself once a new instance is create. It can take in 0 arguments if the parameter is not given. In our example, 1 parameter is given.

@name is an instance variable. By attaching a @ in from of a variable it becomes an instance variable. So what is the different between a variable and an instance variable? Scope. A normal variable is only visible inside of a method in which it was created. Instance variable is that, they are visible everywhere in the object.

There is also a class variable @@class_var which is like a global variable $global_varbut only within the class.

Our new cat instance…

cat1 = Cat.new("Charmy")
cat1.name ==> "Charmy
cat1.sound ===> "meow"
cat1.jump ===> "the cat learned how to jump."
cat1.sleep ===> "ZZZzzz"