CODEWITHSUNDEEP
rubyclassmethodsinstance
pankajdoharey
pankajdoharey

Reputation: 1572

Is it suspicious to think that methods go missing in ruby?

class Person
  def name
    puts "Doharey"
  end
end

puts Person.class #=> this out puts Class
puts Class.methods.count #=> 82 methods
puts Person.methods.count #=> 82 methods

In the above example a Person class is created which inherits from Class and both Person and Class has equal number of methods.

Now lets instantiate Person class

a = Person.new
puts a.methods.count #=> 42 methods

If a is an instance of Person then why are the number of methods less in a than Person. What happens ? how some methods go missing ? Are they not inherited in the first place ? If so how ?

Upvotes: 1

Views: 89

Answers (2)

Lars Haugseth
Lars Haugseth

Reputation: 14881

class Person
  def name
    puts "Doharey"
  end
end

How many instance methods are there in our new class?

Person.instance_methods.size
# => 72

List all instance methods of a class, excluding any methods inherited from the superclass:

Person.instance_methods(false)
# => [:name]

Every new class is by default a subclass of Object:

Person.superclass
# => Object

How many instance methods are there in the superclass?

Object.instance_methods.size
# => 71

Upvotes: 1

Julik
Julik

Reputation: 7856

 a.methods

are the instance methods and

 Person.methods

are class methods. They do not share the same namespace. When you define name on Person you are defining an instance methods.

class Person
  def self.name
    puts "Doharey"
  end
end
=> nil
Person.methods.count
=> 113
Class.methods.count
=> 114

Here I've defined a class method which also shows up in the method list.

Upvotes: 2

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