CODEWITHSUNDEEP
ruby
sawa
sawa

Reputation: 168081

Why can an instance method be called as a module method after include?

An instance method defined on a module:

module A
  def foo; :bar end
end

seems to be able to be called as a module method of that module when that module is included:

include A
A.foo # => :bar

Why is that?

Upvotes: 3

Views: 126

Answers (2)

Shawn Balestracci
Shawn Balestracci

Reputation: 7530

You're including A into Object. 

module A
  def self.included(base)
    puts base.inspect #Object
  end

  def foo
    :bar
  end
end

include A

puts A.foo # :bar
puts 2.foo # :bar

#puts BasicObject.new.foo   #this will fail

Also note that the top level object main is special; it's both an instance of Object and a sort of delegator to Object.

See http://banisterfiend.wordpress.com/2010/11/23/what-is-the-ruby-top-level/

Upvotes: 6

kmanzana
kmanzana

Reputation: 1198

Tried this out in irb, it included it in Object. include A also returns Object

irb > module A
irb >   def foo; :bar end
irb > end
 => nil 
irb > Object.methods.include? :foo
 => false
irb > include A
 => Object
irb > Object.methods.include? :foo
 => true

Upvotes: 0

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