Ruby Private Class Methods

Today I learner that Ruby Module has private_class_method, this way we can for example make the new method as private on service objects:

class MyServiceObject
  private_class_method :new

  def self.call(*args)
    new(*args).call
  end

  def initialize(foo:)
    @foo = foo
  end

  def call
    @foo
  end
end

Note that in this example the new method is private, so the .call will work, but the .new().call will raise an error:

irb> MyServiceObject.call(foo: "FOO")
=> "FOO"

irb> MyServiceObject.new(foo: "FOO").call
NoMethodError: private method `new' called for MyServiceObject:Class