ios - How do I access the dealloc method in a class category? -

ios - How do I access the dealloc method in a class category? -

i need perform action in dealloc method of category. i've tried swizzling doesn't work (nor great idea).

in case asks, reply no, can't utilize subclass, category.

i want perform action on delay using [nstimer scheduledtimerwithtimeinterval:target:selector:userinfo:repeats:] or [self performselector:withobject:afterdelay:] , cancel on dealloc.

the first issue nstimer retains target, don't want. [self performselector:withobject:afterdelay:] doesn't retain, need able phone call [nsobject cancelpreviousperformrequestswithtarget:selector:object:] in dealloc method or crash.

any suggestions how on category?

i stumbled on solution haven't seen before, , seems work...

i have category that--as 1 does--needs state variables, utilize objc_setassociatedobject, this:

memento *m = [[[memento alloc] init] autorelease]; objc_setassociatedobject(self, kmementotagkey, m, objc_association_retain_nonatomic);

and, needed know when instances category extending beingness dealloced. in case it's because set observers on self, , have remove observers @ point, otherwise nskvodeallocatebreak leak warnings, lead bad stuff.

suddenly dawned on me, since associated objects beingness retained (because of using objc_association_retain_nonatomic), must beingness released also, , hence beingness dealloced...in fact had implemented dealloc method in simple storage class had created storing state values. and, postulated: my associated objects must dealloced before category's instances are! so, can have associated objects notify owners when realize beingness dealloced! since had retained associated objects, had add together owner property (which not specified retain!), set owner, , phone call method on owner in associated object's dealloc method.

here's modified part of category's .m file, relevant bits:

#import <objc/runtime.h> // can utilize objc_setassociatedobject, etc. #import "targetclass+category.h" @interface targetclass_categorymemento : nsobject { glfloat *_coef; } @property (nonatomic) glfloat *coef; @property (nonatomic, assign) id owner; @end @implementation targetclass_categorymemento -(id)init { if (self=[super init]) { _coef = (glfloat *)malloc(sizeof(glfloat) * 15); } homecoming self; }; -(void)dealloc { free(_coef); if (_owner != nil && [_owner respondstoselector:@selector(associatedobjectreportsdealloc)]) { [_owner associatedobjectreportsdealloc]; } [super dealloc]; } @end @implementation targetclass (category) static nsstring *kmementotagkey = @"targetclass+category_mementotagkey"; -(targetclass_categorymemento *)targetclass_categorygetmemento { targetclass_categorymemento *m = objc_getassociatedobject(self, kmementotagkey); if (m) { homecoming m; } // else m = [[[targetclass_categorymemento alloc] init] autorelease]; m.owner = self; // can allow owner know when dealloc! objc_setassociatedobject(self, kmementotagkey, m, objc_association_retain_nonatomic); homecoming m; } -(void) dostuff { ccsprite_blurablememento *m = [self ccsprite_blurablegetmemento]; // stuff needed category for, , store state values in m } -(void) associatedobjectreportsdealloc { nslog(@"my associated object beingness dealloced!"); // stuff need when category instances dealloced! } @end

the pattern here learned somewhere (probably on s.o.) uses mill method or create memento object. sets owner on memento, , memento's dealloc method calls allow owner know it's beingness dealloced

caveats:

obviously, have have associated object set objc_association_retain_nonatomic, or won't retained , released automatically. this becomes trickier if memento/state associated object gets dealloced under other circumstances owner beingness dealloced...but can train 1 object or other ignore event. the owner property can't declared retain, or you'll create strong reference loop , neither object ever qualify dealloced! i don't know it's documented objc_association_retain_nonatomic associated objects released before owner dealloced, seems happen way , must case, intuitively @ least. i don't know if associatedobjectreportsdealloc called before or after targetclass's dealloc method--this important! if runs afterwards, if seek access fellow member objects of targetclass crash! , guess it's afterwards.

this little messy, because you're double-linking objects, requires careful maintain references straight. but, doesn't involve swizzling, or other interference runtime--this relies on behavior of runtime. seems handy solution if have associated object. in cases might worth creating 1 grab own deallocs!

ios objective-c cocoa-touch memory-management nstimer