From: Stefano Crocco <stefano.crocco@...>
Date: 2007-11-16T00:11:03+09:00
Subject: Re: Struct constructor

Alle giovedì 15 novembre 2007, Wayne Magor ha scritto:
> It isn't possible to define a class method [] (to make a constructor)
> for a struct is it?
>
> If you have:
>
>      Customer = Struct.new( "Customer", :name, :address, :zip )
>      joe = Customer.new( "Joe Smith", "123 Maple, Anytown NC", 12345 )
>
> but you want it to be:
>
>      joe = ["Joe Smith", "123 Maple, Anytown NC", 12345]
>
> Ruby will just make joe an array, right?  No way around this that I
> can see, is there?

You can't instruct ruby to create a class different from Array for the [x, 
y, ...] construct, but you can define a [] method for a class, and use it to 
create a new istance of the class:

class A
 
 def initialize x, y
   @x = x
   @y = y
 end

 def A.[](x, y)
  new x, y
 end

end

a = A[1, 2]

Since your Customer class was created using Struct.new, it already provides 
this feature (at least, my trials show this, although I couldn't find 
documentation about this). So, you can write:

joe = Customer["Joe Smith", "123 Maple, Anytown NC", 12345 ]

I hope this helps

Stefano