call function of class instance with no assigned name?

Carl Banks pavlovevidence at gmail.com
Wed May 6 23:48:16 CEST 2009


On May 5, 7:55 pm, Dave Angel <da... at ieee.org> wrote:
> George Oliver wrote:
> > On May 5, 11:59 am, Dave Angel <da... at ieee.org> wrote:
>
> >> 1) forget about getattr() unless you have hundreds of methods in your
> >> map.  The real question is why you need two maps. What good is the
> >> "command string" doing you?   Why not just map the keyvalues directly
> >> into function objects?
>
> > Thanks for the reply Dave. I understand your example and it's what I
> > originally used. Here is more detail on what I'm doing now, I hope
> > this will explain my question better.
>
> > In the game I'm writing the player, monsters, items and so on are
> > instances of class Thing, like:
>
> > class Thing(object):
> >     def __init__(self, x, y, name):
> >         self.x, self.y = x, y
> >         self.name = name
> >         self.brain = None
>
> > Some Things have an instance of class Brain attached. The Brain
> > instance has a list of handlers, like:
>
> > class Brain(object):
> >     def __init__(self):
> >         self.handlers = []
>
> > A handler class defines some functionality for the Brain. Each Brain
> > has an update method like this:
>
> > def update(self, arguments):
> >     for handler in self.handlers:
> >         handler.update(arguments)
>
> > So on each pass through the main game loop, it calls the update method
> > of all the brains in the game, which run their handler update methods
> > to change the state of the game.
>
> > A handler would be something like a key input handler. The key input
> > handler is defined separately from the command handler in the case I
> > want to use a different method of input, for example a mouse or
> > joystick.
>
> > In the dictionary of key inputs I could map each input directly to a
> > function. However there is no instance name I can call the function
> > on, as I create a thing, add a brain, and add handlers to the brain
> > like this:
>
> > player = Thing(26, 16, 'player')
> > player.brain = Brain()
> > player.brain.add_handlers(
> >                             commandHandler(player.brain, player),
> >                             keyboardHandler(player.brain),
> >                             fovHandler(player.brain))
>
> > So what I'm wondering is how to reference the instance in each brain's
> > list of handlers when I want to map something like a key input to a
> > command, or what a better way might be to structure the code.
>
>  >>
>
> >>player.brain.add_handlers(
> >>                            commandHandler(player.brain, player),
> >>                            keyboardHandler(player.brain),
> >>                            fovHandler(player.brain))
>
> You're executing commandHandler, and passing its return value into the
> add_handlers() method.  So commandHandler is a function, not a method,
> and what is its relationship to anything that actually processes commands?

It seems to be a factory function.


> Sorry, your pseudo-code is so far from real code that I can't figure out
> what you're doing.  So I guess I can't be any help till something else
> turns up to make it clearer.  Maybe it's just me.

I think it's you--and probably a lot of other people who haven't ever
written games.  No offense.  As someone who's written games before I
will tell you that George's pseudo-code is not far from real code.
His overall approach is fairly typical of how games handle input,
although there are some problems in the details.


Carl Banks



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