我的isa-swizzling打断KVO

Question

我试图实现，因为我需要在某些对象的dealloc方法中执行一些操作。我正在重写-( class )类；返回原始类的方法(如KVO所做的)。所有操作都很好，直到我尝试将观察者添加到swizzled对象。它只是崩溃了。

1. 0x00000000 ()
2. _NSKeyValueRetainedObservationInfoForObject ()中的0x0091d22a
3. 0x0092ec88 in -addObserver:forProperty:options:context:
4. 0x0092d6fd in -NSObject(NSKeyValueObserverRegistration) addObserver:forKeyPath:options:context:

以下是swizzling的实现

- (void)swizzleClass
{
    NSString *proxyClassName = [NSString stringWithFormat:@"MDSwizzled_%@", NSStringFromClass(self->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->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;
}

MDDummy，它只是一种类保持方法(这和添加原始函数没有什么区别)。

@implementation MDDummy
- (void)dealloc
{

    //Special thinngs

    [super dealloc];
}

- (Class)class
{
    return //original class;
}
@end

编辑：

下面是class_addMethodFromClass函数的实现：

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);
}

Answer 1

您应该看看Mike是如何处理这个问题的：https://github.com/mikeash/MAZeroingWeakRef

摘要:句柄摆动一个KVO-swizzled子类不同-您将不得不修补KVO子类中的KVO方法.