From: Joel VanderWerf <vjoel@...>
Date: 2004-04-26T04:40:22+09:00
Subject: Re: How do I get multiple constructors?

Sam Roberts wrote:
> I'm aware of the case where you have a few constructors, but they are
> implemented as some kind of "syntax sugar" on top of one constructor
> that does all the work (the example from "Singletons and other
> Constructors" in Pickaxe chapter 3).
> 
> I have two *different* ways of creating an object, and I can't write
> them all in terms of one single constructor. Also, I can't write
> them in terms of public methods of the object (they set up internal
> things that can't be changed by the public).
> 
> I thought I could do this:

You could make them private and use #send to access them from your 
constructors.

>   class Foo
>     private_class_method :new
> 
>   # private :create
>   # private :decode
> 
>     def Foo.create(*args)
         new.send :create, *args
>     end
> 
>     def Foo.decode(*args)
         new.send :decode, *args
>     end
> 
>     def create(a, b)
>       puts "create(#{a},#{b})"
>       self
>     end
> 
>     def decode(a)
>       puts "decode(#{a})"
>       self
>     end

     private :create
     private :decode
>   end
> 
>   Foo.create(1,2)
>   Foo.decode(3)
> 
>   Foo.decode(4).decode(5) # Should NOT work!

Now, the last line gives an error.