Event Handling using Design Patterns & some hard questions

F

firehead.satish

Hello Comp.Lang.C


I have been reading some documentation on the QT 4.0 signalling
systems. I read somewhere that the Signal/Slot systems is based on a
Observer Pattern.

This is where I do not understand. A slot is 'Prototype' that contains
parametres that determines the behaviour of an object.
In this context how can the pattern 'Prototype' become an object
itself?

I am looking for algorithms for implementing an event-handling system
using Design patterns without the use of templates or the use of third
party software.

I know that a Signal is an event which has state therefore an event is
considered a 'State' patttern.
A Command patterns executes a prototype/ slot.

Can a Prototype object specify the behaviour of an event? That is, can
a Prototype pattern specify what Signals/ events are available for an
object such as TextBox or a Button?

How can I specify using design patterns; what parametres are available
for an method?
For example:
button_Clicked methods has no arguments but later on I want to modify
the behaviour, How can I use the Prototype/Command pattern to modify
the behaviour?


The similarity between Signal and Slots with Design Pattern is as
follows.

An observer patterns observes other Observers.
A observer patterns contains many Signals ( State Pattern).
A Signal can contains 1 or many Protoypes/ Command Pattern.

When a observer asynchronously invokes different observer containing a
Signal/State it would then invoke Slots particular to the Signal. For
this to happen I would have to use a Proxy or a Delegate Pattern?

Could someone help out please?



Satish
 
C

Chris Thomasson

Hello Comp.Lang.C [...]
When a observer asynchronously invokes different observer containing a
Signal/State it would then invoke Slots particular to the Signal. For
this to happen I would have to use a Proxy or a Delegate Pattern?

Could someone help out please?

This is not really a C question... It more of an algorithm design question.
You can try 'comp.programming' or something. Anyway, FWIW here is a very
brief diagram of an overview for a multi-threaded event-distribution scheme
I did for some ARM-based embedded devices running Quadros:

http://appcore.home.comcast.net/~appcore/vzoom/msgsys.pdf

I did this in C and ARM assembly language for the thread synchronization
stuff. I used a simple abstract interface method in the implementation (for
the delegate/event/observer data-structures):

http://groups.google.com/group/comp.lang.c/browse_frm/thread/1b106926ba5db19f

I think might be able to help you some wrt creating your event framework in
C. Also, if you plan on using threads in this thing, be sure to post over in
'comp.programming.threads'!

:^)
 
C

Chris Thomasson

Chris Thomasson said:
Hello Comp.Lang.C [...]
When a observer asynchronously invokes different observer containing a
Signal/State it would then invoke Slots particular to the Signal. For
this to happen I would have to use a Proxy or a Delegate Pattern?

Could someone help out please?

This is not really a C question... It more of an algorithm design
question. You can try 'comp.programming' or something. Anyway, FWIW here
is a very brief diagram of an overview for a multi-threaded
event-distribution scheme I did for some ARM-based embedded devices
running Quadros:

http://appcore.home.comcast.net/~appcore/vzoom/msgsys.pdf
[...]

This uses a single distributor thread... If you want to learn how to use
multiple distributors, ask over in 'comp.programming.threads'...
 
A

Al Balmer

Suggestions for redirecting questions are ignored if you try to answer
the question anyway. Let the questioner post in the proper forum and
answer it there.
 

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