Question

I need to create a class that prevents outside code from instantiating it directly. All instances are obtained by calling a couple of class methods, and also some instance methods that will generate new instances and return them.

class SomeClass
  class << self
    private :new, :allocate
  end

  def initialize(hash)
    @hash = hash
  end

  # A class method that returns a new instance
  def self.empty
    new({})   # works fine!
  end

  # Another class method that returns a new instance
  def self.double(a, b)
    new({a => b})   # works fine!
  end

  # An instance method that will generate new instances
  def combine_with(a, b)
    # Here's the problem!
    # Note: it doesn't work with self.class.new either
    SomeClass.new(@hash.merge({a => b}))
  end
end

So I defined the new method to be private. This works for the class methods, inside of them I can still call new internally. But I can’t call new from within the instance methods. I tried defining new as protected, but this didn’t help either.

Answer 1

did you try to use send?

SomeClass.send :new, @hash.merge({a => b})