From: Gavin Sinclair <gsinclair@...>
Date: 2003-11-20T06:33:32+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types)

On Thursday, November 20, 2003, 6:37:50 AM, Sean wrote:

> I'm only talking about checking that a certain interface is present.  Just for 
> the purpose of providing an informative error message when an object which 
> cannot fulfill the needs of a method is passed.  Right now, it just explodes 
> with an ugly message about something that happened deep in the called method.  
> Something more informative would go a LONG way.

Nobody likes undescriptive error messages.  You're asking Ruby to do
something about them, at a cost.  I prefer to believe that the cost
should be on the library developer, who wishes to make life easier for
his clients.

  class LibraryClass
    def library_method
      # code ...
    rescue SpecificError
      # handle it
    rescue => err
      raise LibraryError, "library_method failed: #{err.message}"
    end
  end

Granted, it doesn't often happen in real life, but it is better if the
library author is putting some thought into the user experience,
rather than feeling like he's jumping through hoops to keep an
interface-checker happy.  A frustrated developer probably won't
produce much code; in that case, at least we'd have less cryptic error
messages, I suppose :)

I'm not completely unsympathetic to what you're saying.  In fact, I'd
like to read a detailed RCR.

Cheers,
Gavin