How to make the class constructor private in Ruby?

Question

class A
private
  def initialize
    puts \"wtf?\"
  end
end

A.new #still works and calls initialize

and

class A
private
  def sel         


        

Answer 1

To shed some light on the usage, here is a common example of the factory method:

class A
  def initialize(argument)
    # some initialize logic
  end

  # mark A.new constructor as private
  private_class_method :new

  # add a class level method that can return another type
  # (not exactly, but close to `static` keyword in other languages)
  def self.create(my_argument)
     # some logic
     # e.g. return an error object for invalid arguments
     return Result.error('bad argument') if(bad?(my_argument))

     # create new instance by calling private :new method
     instance = new(my_argument)
     Result.new(instance)
  end
end

Then use it as

result = A.create('some argument')    

As expected, the runtime error occurs in the case of direct new usage:

a = A.new('this leads to the error')