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    <p><em>I still think it would be better to subclass your class and not mess with the runtime, but if you are definitely sure you need to do it in a category, I have an option in mind for you. It still messes with the runtime, but is safer than swizzling I think.</em></p> <p>Consider writing a helper class, say calling it <code>DeallocHook</code> which can be attached to any <code>NSObject</code> and perform an action when this <code>NSObject</code> gets deallocated. Then you can do something like this:</p> <pre><code>// Instead of directly messing with your class -dealloc method, attach // the hook to your instance and do the cleanup in the callback [DeallocHook attachTo: yourObject callback: ^{ [NSObject cancelPrevious... /* your code here */ ]; }]; </code></pre> <p>You can implement the <code>DeallocHook</code> using <code>objc_setAssociatedObject</code>:</p> <pre><code>@interface DeallocHook : NSObject @property (copy, nonatomic) dispatch_block_t callback; + (id) attachTo: (id) target callback: (dispatch_block_t) block; @end </code></pre> <p>Implementation would be something like this:</p> <pre><code>#import "DeallocHook.h" #import &lt;objc/runtime.h&gt; // Address of a static global var can be used as a key static void *kDeallocHookAssociation = &amp;kDeallocHookAssociation; @implementation DeallocHook + (id) attachTo: (id) target callback: (dispatch_block_t) block { DeallocHook *hook = [[DeallocHook alloc] initWithCallback: block]; // The trick is that associations are released when your target // object gets deallocated, so our DeallocHook object will get // deallocated right after your object objc_setAssociatedObject(target, kDeallocHookAssociation, hook, OBJC_ASSOCIATION_RETAIN_NONATOMIC); return hook; } - (id) initWithCallback: (dispatch_block_t) block { self = [super init]; if (self != nil) { // Here we just copy the callback for later self.callback = block; } return self; } - (void) dealloc { // And we place our callback within the -dealloc method // of your helper class. if (self.callback != nil) dispatch_async(dispatch_get_main_queue(), self.callback); } @end </code></pre> <p>See Apple's documentation on <a href="https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html" rel="noreferrer">Objective-C runtime</a> for more info about the associative references (although I'd say the docs are not very detailed regarding this subject).</p> <p>I've not tested this thoroughly, but it seemed to work. Just thought I'd give you another direction to look into.</p>
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    1. POHow do I access the dealloc method in a class category?
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    1. USEgor Chiglintsev
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      1. VTUpMod
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    1. COHow does this inform the class to call the block on call to `dealloc`?
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      1. USGuy Kogus
    2. COhe did write it above: The trick is that associations are released when your target object gets deallocated, so our DeallocHook object will get deallocated right after your object
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      1. USDaij-Djan
    3. COAssociations are automatically released when your object gets deleted, so if no other references to the hook object remain, it will be deallocated as well. The block is called in `-dealloc` of the hook object and that does the trick. It's just an idea and might not work in your case since I'm not sure in what order the `-dealloc` methods would get called on your object and on the hook object, but the whole scheme seems worth a try.
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