From: Jim Cochrane <allergic-to-spam@...>
Date: 2006-11-26T17:15:07+09:00
Subject: Re: coding practise

On 2006-11-25, sempsteen <sempsteen@gmail.com> wrote:
> ok, i get it.
> so when we invoke Hash#has_key? it does not responde by calling and
> getting the result of Hash#[] method, like if [] responds nil has_key
> gives false.
>
>> It also allows for good code readability - 'has_key?': It's pretty
>> obvious to, e.g., a reviewer what the code wants to do.
>
> Yes, i agree with you and i also want to code in the same way. I want
> to learn the best way of doing this.
> Let's say that i want to learn the answer to the ultimate question of
> life, the universe and everything.
> i don't want to make two calls that first one returns true or false
> after 7.5 million years and second one returns the answer another 7.5
> million years later if first one returns true.
>
> puts everything.answer if everything.has_answer?
>

Easy: puts 42

Seriously, I'd say in your above example that the class that
'everything' is an instance of is poorly designed - if 'has_answer' does
the same (redundant) calculation as 'answer'.  (If it doesn't, then
the design is fine and you have to be very, very patient.)  The fix:
change 'has_answer' to store the answer (privately) after calculating it and 
'answer' to simply retrieve that answer if it has been created.

But your hash example is a different matter - if you access the hash a
large number of times and there is redundancy re. 'has_key' vs. [] and
performance is important, it may be worth it to change the app. to not
call has_key.  But if you leave it as is and you find that it performs
acceptably, then IIABDFI (if it ain't broke, don't fix it).

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