From: AdSR <artur_spruce@...>
Date: 2006-12-30T19:00:05+09:00
Subject: Re: Methods validating their arguments: good or bad?

Vincent Fourmond wrote:
> Michael Judge wrote:
> > What do you think?  Do you usually validate your arguments?
>
>   I usually don't, first because I find it makes the code less readable,
> and second because of the performance loss. What I would like, however,
> is something Eifel-like:
>
> def method(a)
> entry_check
>   a.is_a(String)
> begin
>   # now do something with code
> exit_check
>   # a test on exit
> end
>
>   And the possibility to simply turn it off, that is, completely skip
> over the entry_check and exit_check blocks.
>
>   What do you think ? I think that it would be a marvellous addition to
> Ruby. Of course, that doesn't stop you from writing Test::Units, that
> would be somehow orthogonal.
>
>   Cheers,
>
> 	Vince

What you could do is create a subclass with checking, something like
this (untested):

class Unchecked
  def method(a)
    # do your stuff
  end
end

class Checked < Unchecked
  def method(a)
    # do pre-ckecking
    result = super.method(a)
    # do post-checking
    result
  end
end

Depending on whether you're testing or running in production you'd
switch the actual class used.

If you use this pattern a lot, maybe you could create some general
decorator class (using method_missing etc.) that would allow you to
specify tests for each decorated class or object.

Just a hint. Cheers,

AdSR