From: mental@...
Date: 2005-12-10T06:48:22+09:00
Subject: Re: different methods for initializing one object?

Quoting Mike Fletcher <lemurific+rforum@gmail.com>:

> kibleur.christophe wrote:
> > Hi,
> > let's say I've got a class Point2D to write, it must have 2
> methods to
> > initialize :
> > 1. one with cartesian coordinates i.e : p = Point2D.new(x,y)
> given the
> > numbers x and y;
> > 2. a second with polar coordinates i.e : p =
> Point2D.new(R,theta) given
> > the radius R>0 and an angle theta;
> > How can I manage this ?

If you are always storing cartesian coordinates internally, I'd
suggest introducing a different factory method for creating points
from polar coordinates.  For example:

 class Point2D
   attr_accessor :x, :y

   def initialize( x, y )
     @x, @y = x, y
   end

   def self.new_polar( r, theta )
     new( r * Math::cos( theta ), r * Math::sin( theta ) )
   end
 end

examples:

 cart = Point2D.new( 42, -4 )
 polar = Point2D.new_polar( 3.14159, Math::PI / 4 )

-mental