From: "Mauricio Fernández" <batsman.geo@...>
Date: 2002-11-12T05:55:26+09:00
Subject: Re: What the...?

On Tue, Nov 12, 2002 at 05:47:02AM +0900, Johan Persson wrote:
> Take a look on the snippet below
> 
>   # points is an array of structure-objects defining a point
>   points[0].x = 5
>   points[0].y = 4
>   1.upto(points.length) { |i|
>     points[i].x = points[i-1].x
>     points[i].y = points[i-1].y
>   }
> 
> Now that looks like a legal bunch of statements, right? The thing is
> every time Ruby interpret the line 'points[i].x = points[i-1].x' it
> stops, giving me nothing but a cryptic error message, 'undefined
> method `x=' for nil (NameError)'.
> Could someone please tell me what's going on?

Easy one; when you do points[i].x=... you're calling the 'x=' method of
the points[i] object, which happens to be nil, for points[1] == nil.
You're thinking in C++ or Java; Ruby uses accessors.


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