Question

Thread safe NSMutableArray?

Asked by: Geesu

Basically I have my main thread which contains an NSMutableArray, this array is constantly updated/changed etc...  on a pretty consistent basis (about every 0.5 seconds).

Declaration in main thread:
NSMutableArray *_list = [NSMutableArray array];

I'd like for my second thread to ONLY read data from this array, so I decided to return a COPY of the NSMutableArray as NSArray:
NSArray *list = [[_list copy] autorelease];

But i'm getting a crash:
Thread 4 Crashed:
0   com.apple.CoreFoundation            0x9423bb7e __CFTypeCollectionRetain + 174
1   com.apple.CoreFoundation            0x9428b330 CFArrayCreateCopy + 304
2   com.apple.Foundation                0x93858ebd -[NSCFArray copyWithZone:] + 49
3   com.apple.CoreFoundation            0x9429aa5a -[NSObject(NSObject) copy] + 42

Any ideas?

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Asked On
2009-09-12 at 12:03:43ID24727080
Tags

Cocoa

Topics

Apple Programming

,

Objective-C Programming Language

Participating Experts
1
Points
500
Comments
3

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Answers

 

by: fridomPosted on 2009-09-13 at 23:05:56ID: 25323123

May I ask why you do not put writing to that array into an syncronize construct?

Regards
Friedrich

 

by: GeesuPosted on 2009-09-14 at 05:53:14ID: 25324856

Can you explain further?

 

by: fridomPosted on 2009-09-14 at 06:48:06ID: 25325340

See e.g
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/Multithreading/ThreadSafety/ThreadSafety.html#//apple_ref/doc/uid/10000057i-CH8-SW1

I would use the @synchronice stuff for that

so just write something like

myInsertIntoArray(NSMutableArray *arr; NSObject obj, int index) {
           @synchronized(arr);
           {
                 [arr insertObject: obj atIndex: index];
           }
}
 
That's all there is...
                                              
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