Ruby private class method

The follwing is just so I can remember it... You need not read all this.

In Java, if you need a class whose constructor is private - so you can’t instantiate it from anywhere else (.but not a Singleton too) , you'd do:

public class AClass {
private int a;
private AClass(int a){
super();
this.a = a;
}
}

In Ruby, it's a bit different. The why will come later (dynamism of Ruby), but just hiding the initialize method is not enough. You can still create an object coz you are actually calling the new method:
irb(main):001:0> class AClass
irb(main):002:1> attr_reader :a
irb(main):003:1> private
irb(main):004:1> def initialize(a)
irb(main):005:2> @a = a
irb(main):006:2> end
irb(main):007:1> def some_other_method
irb(main):008:2> "ha"
irb(main):009:2> end
irb(main):010:1> end
=> nil
irb(main):011:0> obj = AClass.new(100)
=> #
irb(main):012:0> obj.a
=> 100
irb(main):013:0> obj.some_other_method
NoMethodError: private method `some_other_method' called for #
from (irb):13
from :0
irb(main):014:0>


You'd have to hide the new method:

class AClass
attr_reader :a
def initialize(a)
@a = a
end
def self.test
"test"
end
private_class_method :test
end

puts AClass.test


that shows:
test.rb:12: private method `test' called for AClass:Class (NoMethodError)