Re: Locking from within an enumerator
Re: Locking from within an enumerator
- Subject: Re: Locking from within an enumerator
- From: James Chen <email@hidden>
- Date: Wed, 21 Apr 2004 10:11:18 +0800
Hi,
Base on your original logic; when caller query the enumerator, you lock
the data model. And unlock it after the enumerator dealloc.
Your approach is making the critical section as long as the
enumerator's life.
How about this. When caller query the enumerator, you return the
enumerator after locking the data model successfully. And force the
caller to call other method to unlock the data model.
This has a short coming which makes the object a little unfriendly.
-----------------------------------------------------------Data Model
- (NSEnumerator*)lockModelAndGetEnumerator
{
if (m_InternalLock tryLock) { // lock or tryLock based on your strategy
return [dataArray objectEnumerator];
} else
return nil;
}
- (void)unlock
{
[m_InternalLock unlock];
}
-----------------------------------------------------------Thread
- (void)doSomething
{
NSEnumerator *enumerator = [dataModel lockModelAndGetEnumerator];
if (enumerator) {
id obj;
while (obj = [enumerator nextObject]) {
[obj doSomethingElse];
}
[dataModel unlock];
}
}
HTH,
James
I have a data model that can be accessed by multiple threads at once.
It is basically an array of stuff. I want to be able to allow threads
to iterate over the data model, and so I was thinking of creating an
NSEnumerator subclass that locks the model for the duration of the
enumerator's life. The problem with this is that I don't know when the
NSEnumerator will have its dealloc called (actually, I don't even know
if dealloc is really ever called - I put NSLogs in - (void) dealloc
before, but the NSLogs never print out).
Anyway, back to the main point, assuming dealloc is eventually called,
I'm not sure if I can depend on that behavior to call unlock for me.
Does anyone have a better obj-c design pattern for iterating over an
array in a multithreaded environment?
Mike
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