Object Methods:

• Object Methods are thode methods which we have to explicitly define in the class.
• First we have to create an object of the class and then we call the object methods.

Example:

class Object
  def initialize (name)
    @name=name
  end
  def display
    puts @name
   end
end
obj = Object.new("Rahul")   #creating the object of the class
obj.display

Output:   Rahul

Class Methods:

• Class Methods are those methods which are implicitly defined in the class itself.
• We do not have to define the class methods on our own.
• For class methods we do not have to create objects for them.
• They are called directly by using the name of the class.

Example:

class Apple 
  def self.fruit #self is a class method
    puts "An Apple is an healthy fruit" 
  end 
end 

Apple.fruit #Invoking the fruit method by using the name of the class Apple 

Output: An Apple is an healthy fruit

• As we can see in that fruit is a method of the Apple class.
• Self is a class method which is defined on the fruit method definition.
• Another way of writing the class method is :

class Apple

  class << self         #Another way of writing the class method
    def fruit
      puts "An Apple is an healthy fruit"
    end
  end
end