From: David Garamond <davegaramond@...>
Date: 2003-01-20T22:00:51+09:00
Subject: a single class that supports multiple facets/interfaces

i want to have a class that can support multiple sets of methods, based 
on what the client requests. so far i have written the following python 
code. it's ugly/not elegant and i haven't managed to come up with a less 
ugly ruby version :-)

<<EOF
class C:
     def foo(self):
         print "foo"
     def bar1(self):
         print "bar version 1"
     def bar2(self, arg):
         print "bar version 2, arg =", arg
     def facet(self, whichFacet=1):
         if whichFacet == 1:
             return C_facet1(self)
         elif whichFacet == 2:
             return C_facet2(self)
         return

class C_facet1:
     def __init__(self, c):
         self.foo = c.foo
         self.bar = c.bar1

class C_facet2:
     def __init__(self, c):
         self.foo = c.foo
         self.bar = c.bar2

c1 = C().facet(1) # client1 picks interface1
c1.foo()          # prints "foo"
c1.bar()          # prints "bar version 1"

c2 = C().facet(2) # client2 picks interface2
c2.foo()          # prints "foo"
c2.bar(123)       # prints "bar version 2, arg = 123"
EOF

if a client wants interface 1, then she will get the methods foo and bar 
(which is actually C#bar1). if he picks interface 2, then she will get 
the methods foo and bar (which is actually C#bar2). for all she cares, 
she just wants to know/deal with a single [versatile] class, C. and from 
that single class, she can pick several sets of features/interfaces she 
needs/wants.

i know that, in ruby, modules are usually used for things like this, but 
in my case many of the method names are the same so i don't think 
modules are approriate for this. for example, interface1 consists of 
foo, bar, baz, abc, and abd. interface2 consists of foo, bar, baz, bab, 
bac. in most of the cases all of the interfaces provide the same set of 
features, just in a different style or different revision.

any pointers of how i might do something like this in ruby?

-- 
dave