From: Gavin Sinclair <gsinclair@...>
Date: 2004-10-06T10:36:43+09:00
Subject: Re: A ruby course

On Wednesday, October 6, 2004, 3:24:12 AM, Brian wrote:

> Hello Group,

> I need more help.

> Gavin Sinclair wrote:
>> 
>> p51. Good exercise.  How about another?
>> 

> Anybody has an idea for an exercise on extending existing classes. So
> far the only thing I have come up with is:

> \exercise{Fibonacci II}{
>    Extend \codetype{Integer} with a function fib that calculates the
>    corresponding fibonacci number.}

> And my creativity is at an all time low.

There are plenty of examples at http://extensions.rubyforge.org.  I
was thinking of something like String#indent as an exercise, but you
haven't taught regexen at this point, so that's out.  But something
else might do.

>> p52. It would be good to teach extending objects, because it's core to
>>      Ruby, and important when understanding "class methods".  But you
>>      can emphasise that it's advanced material, so students needn't be
>>      worried if they don't get it straight away.  (It's not *that*
>>      hard to accept, anyway... :)
>> 

> Anybody nows of a good example where it is neccessary to extend an 
> existing object?

> I have never used this feature and I don't know when to use it in a 
> sensible way.

It could be something academic like changing the to_s output for a
particular array/string.  But really, the main point of this feature
(adding methods to objects) is to add methods to classes (which are
objects).  So perhaps use that as an example.

>> p55. Missing exercises.

> Somebody has an idea for an exercise on using modules (as namespace and
> mixin?)

A favourite of mine is building a new class, then mixing in Enumerable
and Comparable.  So you're not building a new module, but reusing two
existing ones.

Gavin