properties and get/set methods

[John Roth]

"Mike C. Fletcher" <mcfletch at rogers.com> wrote in message
news:mailman.1049604615.22077.python-list at python.org...
> Dan Bishop wrote:
>
> >Timothy Grant <tjg at craigelachie.org> wrote in message
news:<mailman.1049581810.25706.python-list at python.org>...
> >
> >
> ...
>
> >>Is it possible to determine which attribute was used to as the
trigger for the
> >>call to setvar() or getvar()? so that set_appropriate_attribute() or
> >>appropriate_attribute() can set the correct attribute or get the
correct
> >>attribute?
> >>
> >>
> >
> >Why not just use two different getvar and setvar functions?
> >
>
> When you're doing generic "framework" level programming, it's just not
> acceptable to have to define 2 (really 3) new functions for every
> property.  Compare:
>
>     def setMyProperty( self, value ):
>        do_the_generic_thing( self, 'myProperty', value)
>        self.__dict__["myProperty"] = value
>     def getMyProperty( self ):
>        do_the_generic_thing( self, 'myProperty', value)
>        return self.__dict__["myProperty"]
>     def delMyProperty( self ):
>        del self.__dict__[ "myProperty" ]
>     myProperty = property( getMyProperty, setMyProperty,
delMyProperty,
> """Some documentation""")
>
> versus:
>
>     myProperty = StringProperty(
>        "myProperty", """Some documentation""",
>        defaultValue = "this value",
>     )
>
> In these cases, you're using properties to simplify the modelling of
> domain objects, or to provide some *generic* functionality over and
> above a regular value get/set.  You don't want to have to specify that
> functionality for every property, you just want to say "this is one of
> _those_ properties".  The code bloat (not to mention mindless
> duplication of code) when you get up to 15 or 20 properties for an
> object would be ridiculous.

Well, I suppose since this is Sunday, it's appropriate to bring
religion into it.

John Roth
>
>
> Enjoy,
> Mike