Singleton method vs. class method

Question

Are class method and singleton method doing the same or different? Here is an example.

class C
  def self.classmethod
    puts "class method #{self}"
  end
end

C.classmethod  # class method C
c = C.new

def c.singletonmethod
  puts "instance method #{self}"
end

c.singletonmethod  # instance method #<C:0x0000000118ed08>

Answer 1

Most of what happens in Ruby involves classes and modules, containing definitions of instance methods

class C
  def talk
    puts "Hi!"
  end
end

c = C.new
c.talk
Output: Hi!

But as you saw earlier (even earlier than you saw instance methods inside classes), you can also define singleton methods directly on individual objects:

obj = Object.new
def obj.talk
  puts "Hi!"
end
obj.talk
#Output: Hi!

When you define a singleton method on a given object, only that object can call that method. As you’ve seen, the most common type of singleton method is the class method—a method added to a Class object on an individual basis:

class Car
  def self.makes
    %w{ Honda Ford Toyota Chevrolet Volvo }
  end
end

But any object can have singleton methods added to it. The ability to define method- driven behavior on a per-object basis is one of the hallmarks of Ruby’s design.

Singleton classes

Singleton classes are anonymous: although they’re class objects (instances of the class Class ), they spring up automatically without being given a name. Nonetheless, you can open the class-definition body of a singleton class and add instance methods, class methods, and constants to it, as you would with a regular class.

Note:

Every object has two classes:

■ The class of which it’s an instance

■ Its singleton class

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At Last I would highly recommends you to watch.

1: The Ruby Object Model and Metaprogramming For detail info about singleton method vs. class method ruby

2: MetaProgramming - Extending Ruby for Fun and Profit - by Dave Thomas

Hope this help you!!!