From: "R. Kumar" <sentinel.2001@...>
Date: 2010-02-02T00:10:09+09:00
Subject: Re: Inheritance related problem

Rick Denatale wrote:
> On Mon, Feb 1, 2010 at 1:54 AM, R. Kumar <sentinel.2001@gmx.com> wrote:
>>> I'm having trouble understanding how you got into this position. �I'm
>>
>> att=Ncurses::A_NORMAL
>> � � �super(row - @top, col - @left, height, width, �color, att)
>> � �end
>>
>> Now in the parent Window, print_border does a call to printstring to
>> reset the background. Unfortunately, the child's printstring gets called
>> and @top and @left get decremented again.
> 
> So why not just factor out what's different between Parent and Child
> 
> class Parent
>   def printstring(row, col, ... other parameters omitted)
>       row, col = *transform(row, col)
>       # do whatever you need
>   end
> 
>   def transform(row, col)
>      [row, col]
>   end
> end
> 
> class Child < Parent
>    def transform(row, col)
>        [row - @top, col - @left]
>    end
> end
> 

Aah, there are more such methods.

SO in the second method print_border which happens to call printstring I 
would save row, col for the next call.

> class Parent
>   def print_border(row, col, ... other parameters omitted)
>-       row, col = *transform(row, col)
>+       nrow, ncol = *transform(row, col)
>       # do whatever you need with nrow and ncol
>+       printstring row, col # using original args
>   end

Looks good, will give it a try. I feel there's still something "off" in 
what i've done, and the question I am asking you, since it requires the 
parent to protect itself from (or know of) misbehaviour from a child.

The overriding in Child was tacked on hastily and worked great till i 
noticed some cases where an extra line was getting erased.

Thanks a lot.
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