From: Alex Young <alex@...>
Date: 2006-12-30T21:13:41+09:00
Subject: Re: Methods validating their arguments: good or bad?

Michael Judge wrote:
> 
> Code Complete* recommends that methods validate the arguments they 
> receive.  The author went on to say that in a 1984 study, researchers 
> discovered that miscommunication between routines caused 39% of the 
> programming errors observed.  The idea is that, if we check our 
> arguments before using them, bad data won't flow through undetected, 
> causing even vaguer problems later on.  Lucky for us, Ruby checks the 
> number of arguments received against the method definition -- finding 
> many of these problems at the time they're written.  But checking that 
> the arguments make sense are still our responsibility.  Should we do 
> it?  Is it too much overhead for too little gain?
> 
>  From the Rails source:
> 
> def select_tag(name, option_tags = nil, options = {})
>   content_tag :select, option_tags, { "name" => name, "id" => name 
> }.update(options.stringify_keys)
> end
> 
> The arguments to select tag are really easy to screw up.  Adding code to 
> validate them would add four or five lines to this terse method.  Plus 
> it would probably need a few helper methods just to remain readable.  
> But it would also prevent programmers from wasting huge amounts of time 
> hunting for why their browser rendered a bad select box.  The argument 
> for adding validation is really strong for any non-trivial project, but 
> does it ruin Ruby's elegance?
> 
> What do you think?  Do you usually validate your arguments?
> 

This has come up before:

http://www.erikveen.dds.nl/monitorfunctions/index.html#6.2.0

I do it (not always this way), but not often enough...

-- 
Alex