| Re: object methods as friends [message #39165 is a reply to message #38969] |
Sun, 18 April 2004 15:42  |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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Zorch Tierod wrote:
> Hey there,
> I've got an application that uses two types of objects, each with
> several different method procedures.
>
> What I'm trying to do is to calculate some stuff based on the
> interaction of one of the objects with an array of the other type of
> objects. Illustrative example (but not the REAL application!):
>
> sb = {bullet, param1:.....} ;protoype for bullet object
> st = {target, param1:......} ;prototype for target object
>
> target_array = obj_arr('target',10) ;make a bunch of targets
> projectile = obj_new('bullet') ;make a bullet
>
> jtarget = which_hit(target_array, projectile) ;return which target is
> hit
>
> My problem seems to be that the function 'which_hit' has no access to
> the data of either the 'bullet' or the 'target' objects, because it is
> not a method of either - and I can't make it a method of both...
The standard way of dealing with this in IDL is to expose the properties
you need via GetProperty & SetProperty methods. Yes, this can be a lot
of work and, no, it doesn't allow for discrimination between friend and
non-friend callers.
I suppose you could have FriendGetProperty & FriendSetProperty methods
which asked for authentication from the caller, but really, why would
you bother? If you don't want non-friends to access certain properties,
then just don't do it.
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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