Memory Management

Lightening talk done at NSLondon about Memory Management. Covering many of the common mistakes people have with memory management using ARC and how to avoid. Briefly covering the runtime support for ARC.

Related blog post: http://kylefuller.co.uk/posts/memory-management-arc/

Transcript

1. Memory Management
   

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2. -[NSObject retainCount]
   

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3. Retainable Object
   Pointers
   

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4. Object Pointers
   id
   Class
   NSObject
   __attribute__((NSObject))
   

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5. __attribute__((NSObject))
   

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6. dispatch_queue_t
   

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7. @property (nonatomic, strong)
   dispatch_queue_t queue;
   

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8. Ownership
   Qualification
   

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9. __unsafe_unretained
   

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10. __strong
    

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11. __autoreleasing
    

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12. __weak
    

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13. id objc_storeWeak(id *object, id value)
    

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14. objc_clear_deallocating
    

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15. objc_arc_weak_unavailable
    

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16. Property Declarations
    assign __unsafe_unretained
    copy -copy + __strong
    retain __strong
    unsafe_unretained __unsafe_unretained
    weak __weak
    

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17. Blocks
    

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18. `strong` vs `copy`
    

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19. Always use copy
    

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20. @property (nonatomic, copy)
    

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21. dispatch_block_t block = ^{
    NSLog(@"Hello World!");
    };
    !
    NSArray *blocks = [[NSArray alloc] initWithObject:[block copy]];
    

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22. Retain Cycle
    

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23. - (void)startOperation {
    NSOperation *operation = [[NSOperation alloc] init];
    !
    [operation setCompletionBlock:^{
    NSLog(@"Completion for %@", operation);
    }];
    }
    

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24. Operation Completion Handler
    

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25. - (void)startOperation {
    NSOperation *operation = [[NSOperation alloc] init];
    __weak NSOperation *weakOperation = operation;
    !
    [operation setCompletionBlock:^{
    NSLog(@"Completion for %@", weakOperation);
    }];
    }
    

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26. The Dealloc Problem
    

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27. Releasing UIKit objects
    in background threads
    

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28. CoreFoundation is not
    subject to ARC
    

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29. CFRelease(stringRef);
    

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30. UIColor *whiteColor = [UIColor whiteColor];
    CGColorRef whiteRef = [whiteColor CGColor];
    !
    // Crash when using whiteRef
    

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31. UIColor *whiteColor = [UIColor whiteColor];
    CGColorRef whiteRef = CGRetain([whiteColor CGColor]);
    !
    // Use whiteRef
    !
    CGRelease(whiteRef);
    

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32. Exceptions
    

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33. -fobjc-arc-exceptions
    

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34. Fast Enumeration
    

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35. for (const __strong NSObject *object in objects) {
    NSLog(@”Object: %@”, object);
    }
    

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36. Faster Enumeration
    

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37. for (const __unsafe_unretained NSObject *object in objects) {
    NSLog(@”Object: %@”, object);
    }
    

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38. Does this actually have
    any real world benefits?
    

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40. KFNumber
    

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41. Tagged Pointer
    

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43. Twitter: @kylefuller
    GitHub: kylef
    !
    http://kylefuller.co.uk/
    

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