CODEWITHSUNDEEP
ruby
Incerteza
Incerteza

Reputation: 34924

private and private_class_method keywords in Ruby

Why does private is applicable only for instance methods and isn't for the class methods? Not only that, why doesn't private_class_method method make the class methods private?

class Foo

  private

  def self.private_class_method
    puts 'hello from private_class_method'
  end


  def private_instace_method
    puts 'hello from private_instace_method'
  end
end

Foo.private_class_method #Ok!
Foo.new.private_instace_method #error: private method `private_instace_method' called for #<Foo:0x000001020873b8>

How about this?

class Foo

  private_class_method :private_class_method

  def self.private_class_method
    puts 'hello from private_class_method'
  end

  private

  def private_instace_method
    puts 'hello from private_instace_method'
  end
end

Foo.private_class_method #Ok!
Foo.new.private_instace_method #error: private method `private_instace_method' called for #<Foo:0x000001020873b8>

How do I make a class method private?

Upvotes: 3

Views: 1998

Answers (1)

spickermann
spickermann

Reputation: 106972

You can create a private class methods like this:

class Foo
  def self.will_be_private
    # ...
  end
  private_class_method :will_be_private
end

Or like this:

class Foo
  class << self
  private
    def will_be_private
      # ...
    end
  end
end

While it is possible the make a class methods private, I can hardly think of a good reason to do so. IMO a private class method is a code smell and indicates that there is a thing that should be extracted into it own class.

Upvotes: 5

Related Questions