Ruby Class Cheat-Sheet




Class names begin with a capital letter after the class keyword and terminate with the keyword end:

# Class
class MySuperClass
    def mySuperMethod
        puts 'print something' 
    end
end 
 
# Class Inheritance:
class MyExtendedClass < MySuperClass
    def extendedClassMethod
        puts 'print something from the extended class' 
    end
end

myObject1 = MySuperClass.new
myObject2 = MyExtendedClass.new
 

Methods (functions) start with a lowercase letter after the def keyword and terminate with the keyword end.

Creating objects Example:

class Dog  
    def talk   
        puts 'Woof!'  
    end  
end
  
class Terriers < Dog  
    def howl
        puts 'wooooooooooooooo!!!'  
    end  
end  
  
myDog = Terriers.new  
yourDog = Dog.new  

Class Instance variables: A class variable begins with @@ and is shared by all objects created from a class. An instance variable begins with @ and can be accessed only by a specific object.

Constructors: When a class contains a method named initialize this will be automatically called when an object is created using the new method. It is a good idea to use an initialize method to set the values of an object’s instance variables.

Example:

class Dog

    @@num_dogs = 0

    # This is a class method
    def Dog.showInfo
        puts 'TNumber of dogs = ' +@@num_dogs.to_s 
    end
  
    def talk   
        puts 'Woof!  Name is ' + @name + ' I'm 1 of ' +@@num_dogs.to_s
    end  

    def initialize ( aName )
        @name = aName
        @@num_dogs += 1
    end
end
  
class Terriers < Dog  
    def howl
        puts @howl
    end

    def initialialize ( aName, aHowl )
        super (aName)
        @howl = aHowl
    end  
end  

myDog = Dog.new ( 'Bob' )
yourDog = Terries.new ('Fido', 'wooooooooooooo!!!' )

myDog.talk
yourDog.howl
Dog.showInfo

Parenthesis are optional


Published by

Ferdy Mañago

Portland, Oregon