From: Chad Fowler <chad@...>
Date: 2003-11-21T01:58:11+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata about attribute types)

qyyOn Thu, 20 Nov 2003, Sean O'Dell wrote:

# 
# A contract is any interface, and a Ruby class is an interface.  True, a Ruby 
# class isn't the definition of a contract, but any OO class serves the 
# function well enough.  Despite Ruby's flexibility, at any given point, a 
# class implements an interface.  It can be extended or changed, but it 
# definitely describes an interface.
# 
# Because no type checking at all causes non-descriptive errors when an object 
# is passed to a method (2 of 1 parameters?) which expects it to have certain 
# methods which takes certain parameters.  Either way, an error occurs, but 
# with some form of type checking, the programmer gets a much clearer picture 
# of why they can't pass in a particular object to a method without at least 
# some modification.



# 
# Example: you get an "object does not the :socket interface."  You then say to 
# yourself:  "Ah!  This library wants something like the Socket class...okay, I 
# can fake that!"


Or how about:

blah.rb:7:in `example_method': undefined method `drive' for "car":String 
(NameEr
ror)
        from blah.rb:10           

Is there ever a chance you wouldn't understand what that means?  
Personally, I would see that message, open up blah.rb, look at line 10 

Or 
# 
# It's just informational.  It's just for the purpose of speeding up development 
# and making the code a little more robust through a good report of what is 
# going wrong when someone passes in an object that can't be used by the 
# method.  It doesn't prove that an object correctly implements an interface, 
# and the object can definitely break the interface, but the facility would be 
# there for programmers who can make use of it.  For those that tend to break 
# interfaces when programming rather than use them properly, there are always 
# QA jobs.  =)
# 
# 	Sean O'Dell
# 
#