[Newbies] Simple semaphore to synchronize instances of different classes

Wed Aug 15 19:05:28 UTC 2012

Hello Chris !

Thank you for the link. Free books of Stephane Ducasse are inderdeed a
*MUST*.
http://stephane.ducasse.free.fr/FreeBooks.html
(BTW, everybody should consider a little donation to support him)

I'm realizing that my question is unclear.
Let me have a new try in pseudocode.

The problem : synchronizing an instance of a class gameEngine which starts
instances of transition screen / game levels.

Game engine

2012/8/15 <beginners-request at lists.squeakfoundation.org>

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> Today's Topics:
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>    1. Simple semaphore to synchronize instances of different
>       classes (patrick dudjalija)
>    2. Re: Simple semaphore to synchronize instances of different
>       classes (Chris Cunnington)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 14 Aug 2012 21:24:06 +0200
> From: patrick dudjalija <patrick.dudjalija at gmail.com>
> Subject: [Newbies] Simple semaphore to synchronize instances of
>         different       classes
> To: beginners <beginners at lists.squeakfoundation.org>
> Message-ID:
>         <CAEMqm6GttreSY5i+SA=Hg1=
> C8sAszQOu63miV_R5cfAW5a77Sw at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi everybody !
>
> I'm developing an educative game.
> I've written a "gameEngine" class which does the logic for the general
> progression in the game : switching between instances of morph
> subclasses which implement intro screen / mini-games/levels / end
> screen etc ...
>
> Now, i need to synchronize the instance of the gameEngine class with
> the instances of the other classes.
> Example : once the gameEngine starts the instance of a morph subclass
> which implements a mini-game, it must sleep until the mini-game is
> finished, and then wake up and does further required switching (next
> mini-game or intro screen or end screen ...).
>
> i thought that a "simple" semaphore would quickly give a solution to
> the problem.
> But i get a freezed code.
>
> I've modelized/simplified the problem with the following workspace code.
> See also fileout of Class TestSynchro as attachment.
> TestSynchro has a step method which prints some lines to Transcript,
> then calls the method stopStepping and signal to the semaphore.
> The workspace code does a wait, before printing to Transcript 'Hello
> World'!
>
> Problem is that the code freezes , on the line code -> sem wait
> I first thought that the code freezed because in the same process. And
> added a fork to the block which creates instance of TestSynchro. But
> it does'nt help ...
>
> Any help will be appreciated !
> Thanks by advance,
>
> Patrick Dudjalija
>
>
>
> |ts sem|
>
> sem:=Semaphore new.
>
> [ts:= TestSynchro new.
> ts semaphore:sem.
> ts openInWorld.
> ts start.] fork.
>
> sem wait.
> Transcript cr; show:'Hello world !';cr.
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>
> ------------------------------
>
> Message: 2
> Date: Tue, 14 Aug 2012 16:07:36 -0400
> From: Chris Cunnington <smalltalktelevision at gmail.com>
> Subject: Re: [Newbies] Simple semaphore to synchronize instances of
>         different       classes
> To: beginners at lists.squeakfoundation.org
> Message-ID: <502AB008.3030104 at gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> On 12-08-14 3:24 PM, patrick dudjalija wrote:
> > Hi everybody !
> >
> > I'm developing an educative game.
> > I've written a "gameEngine" class which does the logic for the general
> > progression in the game : switching between instances of morph
> > subclasses which implement intro screen / mini-games/levels / end
> > screen etc ...
> >
> > Now, i need to synchronize the instance of the gameEngine class with
> > the instances of the other classes.
> > Example : once the gameEngine starts the instance of a morph subclass
> > which implements a mini-game, it must sleep until the mini-game is
> > finished, and then wake up and does further required switching (next
> > mini-game or intro screen or end screen ...).
> >
> > i thought that a "simple" semaphore would quickly give a solution to
> > the problem.
> > But i get a freezed code.
> >
> > I've modelized/simplified the problem with the following workspace code.
> > See also fileout of Class TestSynchro as attachment.
> > TestSynchro has a step method which prints some lines to Transcript,
> > then calls the method stopStepping and signal to the semaphore.
> > The workspace code does a wait, before printing to Transcript 'Hello
> World'!
> >
> > Problem is that the code freezes , on the line code -> sem wait
> > I first thought that the code freezed because in the same process. And
> > added a fork to the block which creates instance of TestSynchro. But
> > it does'nt help ...
> >
> > Any help will be appreciated !
> > Thanks by ad2vance,
> >
> > Patrick Dudjalija
> >
> >
> >
> > |ts sem|
> >
> > sem:=Semaphore new.
> >
> > [ts:= TestSynchro new.
> > ts semaphore:sem.
> > ts openInWorld.
> > ts start.] fork.
> >
> > sem wait.
> > Transcript cr; show:'Hello world !';cr.
> >
> >
> > _______________________________________________
> > Beginners mailing list
> > Beginners at lists.squeakfoundation.org
> > http://lists.squeakfoundation.org/mailman/listinfo/beginners
>
> http://stephane.ducasse.free.fr/FreeBooks/GuzdialBookDrafts/BuildUI-ch5.pdf
>
> I don't know much about this stuff, but using Semaphore for animations
> seems too low level. Pg. 53 of this pdf describes how step and stepTime
> work.
>
> HTH,
> Chris
>
>
>
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