From: ptkwt@... (Phil Tomson)
Date: 2005-12-06T16:27:33+09:00
Subject: Re: Overloaded constructors in Ruby

In article <20051206012149.EF632339CD@beryllium.ruby-lang.org>,
Kyle Heon <kheon@comcast.net> wrote:
>I have a class that I want to have a number of overloaded constructors for.
>
>I tried doing something like this:
>
>class GravPoint
>    def initialize()
>        this(0, 0, 0, 0, 0)
>    end
>
>    def initialize(x, y, strength)
>        this(x, y, strength, 0, 0)
>    end
>
>    def initialize(x, y, strength, ctime, life)
>        @x, @y, @strength, @ctime, @life = x, y, strength, ctime, life
>    end
>end
>
>When I then run GravPoint.new() I get the following error:
>
>GravPoint.rb:23:in `initialize': wrong number of arguments (0 for 5)
>(ArgumentError)
>
>I think I understand the error, it's expecting 5 arguments (based on the
>last constructor) but I don't the "Ruby" way to set this up. What am I
>missing?
>
>I was able to get this to work, but was hoping that I could do it in a
>format closer to the above to make it a little more flexible to use.
>
>class GravPoint
>    def initialize(x = 0, y = 0, strength = 0, ctime = 0, life = 0 )
>        @x, @y, @strength, @ctime, @life = x, y, strength, ctime, life
>    end

     def GravPoint.from_x_y_strength(x,y,strength)
       new(x,y,strength)
     end

>end


gp = GravPoint.new #matches your first constructor
gp1= GravPoint.from_x_y_strength 5.5,4.2,254  #matches your 2nd c'tor
gp3= GravPoint.new(1,2,3,4,5) #matches your last c'tor

Phil