From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2008-12-03T18:01:28+09:00
Subject: Re: Question about op. overloading

On Wed, Dec 3, 2008 at 9:49 AM, Maarten Mortier
<maarten.mortier@gmail.com> wrote:
> I have:
>
> class Sudoku
>  def[](r,c)
>    @rows[r][c]
>  end
>
>  def set(r,c,a)
>    @rows[r][c]=a
>  end
> end
>
> Now, how can I define a []= operator instead of the awkward set(r,c,a) ?
> I want to be able to do
> sudoku[2,3]=candidate
>
> or even
> sudoku[2][3] = candidate
> and
> sudoku[3] = row
>
> Are these things possible? How, I could not find the information.

A []= operator is possible. It's syntactic sugar for a method named "[]="
and at least two parameters: what's inside the brackets and the
"assigned" value.

An example:


irb(main):001:0> class A
irb(main):002:1> def []= (a,b)
irb(main):003:2> @x[a] = b
irb(main):004:2> end
irb(main):005:1> attr_reader :x
irb(main):006:1> def initialize
irb(main):007:2> @x = {}
irb(main):008:2> end
irb(main):009:1> end
=> nil
irb(main):010:0> a = A.new
=> #<A:0xb7b2bfa8 @x={}>
irb(main):011:0> a[:a] = :b
=> :b
irb(main):012:0> a
=> #<A:0xb7b2bfa8 @x={:a=>:b}>

If you add more parameters to the method, you can use more "keys"
inside the brackets:

irb(main):013:0> class A
irb(main):014:1> def []= (a,b,c)
irb(main):015:2> puts a,b,c
irb(main):016:2> end
irb(main):017:1> end
=> nil
irb(main):018:0> a = A.new
=> #<A:0xb7b070f4 @x={}>
irb(main):019:0> a[:a,:b] = :c
a
b
c
=> :c

Hope this helps,

Jesus.