Re: Sharing variables and inline functions

[Rick Riolo]

I think you want this to be:

inline int getShared (ModelSwarm *this)
{
    return this-> shared;
}
           ^^^^
not "self".

- r


Rick Riolo                           address@hidden
Program for Study of Complex Systems (PSCS)
4477 Randall Lab                
University of Michigan         Ann Arbor MI 48109-1120
Phone: 734 763 3323                  Fax: 734 763 9267
http://www.pscs.umich.edu/PEOPLE/rlr-home.html

On Thu, 4 Mar 1999, Axel von Kamp wrote:

> Date: Thu, 04 Mar 1999 12:07:23 +0000
> From: Axel von Kamp <address@hidden>
> To: address@hidden
> Subject: Re: Sharing variables and inline functions
> 
> I've also been thinking about how to efficiently gain read access to instance
> variables without declaring them as @public. My idea (inspired by what
> C++ does) is that, since in Objective C you can still use functions and gcc
> supports inline functions (which is not ANSI standard), to use inline
> functions for access. I have edited the example below to illustrate what I'm
> talking about
> 
> > > You have the variable you want to share in the class you want to give
> > > write access, for eksample in Modelswarm, and then you implement a
> > > method (in ModelSwarm) to read the variable. Here is an eksample:
> > >
> > > @interface ModelSwarm: Swarm
> > > {
> > >    int  shared;
> > > }
> > > - (int) getShared;
> 
> inline int getShared (ModelSwarm *this);
> 
> > > @end;
> > >
> > > @implementation ModelSwarm
> > > - (int) getShared
> > > {
> > >    return shared
> > > }
> 
> inline int getShared (ModelSwarm *this)
> {
>     return self-> shared;
> }
> 
> > > @end;
> > >
> > > Then you let all your Agents have a reference to the ModelSwarm, that
> > > you have to initialize when you create the Agent objects
> > >
> > > @interface Agent: Swarm
> > > {
> > >    id modelSwarm;
> > > }
> > > - initModel: aModelSwarm;
> > >
> > > and then you can read the shared variable with
> > > [modelSwarm getShared];
> 
> int myInt;
> myInt= getShared (modelSwarm);
> 
> > > /Eric Werk
> > >
> >
> > This's a good idea,but unfortunately the shared variables are all matrixes
> > that are heavely used by each agent.In each step of simulation all the
> > agents have to traverse all the rows of those matrixes.Wouldn't it be an
> > excessive overhead to call every time a method on the ModelSwarm to get
> > the needed row of each matrix?
> 
> This should (?; I'm no compiler expert, so anybody with more technical
> knowledge please comment on this) be as efficient as using a @public instance
> variable without the drawback that @public instance variables can also be
> written to. (Furthermore, @public instance variables are not considered to be
> good style in OO languages.)
> Of course, when you use any functions, you cannot override these as you can
> with messages. But in this case, why would a subclass want to override read
> acces to one of the instance variables of its superclass?
> 
> >
> > Then I was thinking about declaring these matrixes @public in ModelSwarm's
> > interface and the acces their rows as a C structure ,i.e. modelSwarm->row.
> >
> > I tried to do this way modifying the simpleObserverSwarm2 to make each bug
> > print a string declared @public in ModelSwarm  application,but it seems to
> > crash it.Is the latter method correct?
> 
> It should be working. But whenever you use @public you have to make sure that
> when you change the interface of the class which declares a @public instance
> variable, to recompile all modules which access those instance variables. If
> unsure: make clean; make.
> 
> -Axel
> 
> 
> 
> 
>                   ==================================
>    Swarm-Support is for discussion of the technical details of the day
>    to day usage of Swarm.  For list administration needs (esp.
>    [un]subscribing), please send a message to <address@hidden>
>    with "help" in the body of the message.
> 
> 

                  ==================================
   Swarm-Support is for discussion of the technical details of the day
   to day usage of Swarm.  For list administration needs (esp.
   [un]subscribing), please send a message to <address@hidden>
   with "help" in the body of the message.