Databases
StackOverflow2013
Postsdbo
POMy isa-swizzling breaks KVO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POMy isa-swizzling breaks KVO
    primarykey
    data
    text
    <p>I'm trying to implement isa swizzling because I need some actions to happen in dealloc method of certain object. I'm overriding - (Class)class; method to return original class (as KVO does). Everything works fine, until I try to add observer to swizzled object. It just crashes.</p> <ol> <li>0x00000000 in 0x00000000 () </li> <li>0x0091d22a in _NSKeyValueRetainedObservationInfoForObject () </li> <li>0x0092ec88 in -[NSObject(NSKeyValueObserverRegistration) _addObserver:forProperty:options:context:] () </li> <li>0x0092d6fd in -[NSObject(NSKeyValueObserverRegistration) addObserver:forKeyPath:options:context:] ()</li> </ol> <p>Here is implementation of swizzling</p> <pre><code>- (void)swizzleClass { NSString *proxyClassName = [NSString stringWithFormat:@"MDSwizzled_%@", NSStringFromClass(self-&gt;isa)]; Class proxyClass = NSClassFromString(proxyClassName); if (!proxyClass) proxyClass = [self createProxyClassWithName:proxyClassName]; object_setClass(self, proxyClass); } - (Class)createProxyClassWithName:(NSString *)proxyClassName { const char *c_proxyClassName = [proxyClassName cStringUsingEncoding:NSUTF8StringEncoding]; Class proxyClass = objc_allocateClassPair(self-&gt;isa, c_proxyClassName, 0); Class dummyClass = [MDDummy class]; class_addMethodFromClass(proxyClass, dummyClass, @selector(dealloc)); class_addMethodFromClass(proxyClass, dummyClass, @selector(class)); objc_registerClassPair(proxyClass); return proxyClass; } </code></pre> <p>MDDummy it's just a class holding method in convinietn way (there is no difference between this and adding raw functions).</p> <pre><code>@implementation MDDummy - (void)dealloc { //Special thinngs [super dealloc]; } - (Class)class { return //original class; } @end </code></pre> <p>EDIT:</p> <p>Here's implementation of class_addMethodFromClass function:</p> <pre><code>void class_addMethodFromClass(Class class, Class sourceClass, SEL selector) { Method method = class_getInstanceMethod(sourceClass, selector); IMP methodImplementation = method_getImplementation(method); const char *types = method_getTypeEncoding(method); class_addMethod(class, selector, methodImplementation, types); } </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCarl Veazey
    1. USDenis Mikhaylov
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POMy isa-swizzling breaks KVO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POMy isa-swizzling breaks KVO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POMy isa-swizzling breaks KVO
      1. USNikolai Ruhe
      1. VTFavorite
    1. COAre you adding the observer to the object before or after swizzling the class?
      singulars
      1. POMy isa-swizzling breaks KVO
      1. USJustin Spahr-Summers
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload