关于weak 关于KVO-白红宇

weak singleton

+ (id)shareInstance {    static __weak ASingletonClass *instance;    ASingletonClass *strongInstance = instance;    @synchronized(self) {        if (strongInstance == nil) {            strongInstance = [[[self class] alloc] init];            instance = strongInstance;        }    }    return strongInstance;}复制代码

weak associated object

- (void)setContext:(CDDContext *)object {    id __weak weakObject = object;    id (^block)() = ^{
   return weakObject; };    objc_setAssociatedObject(self, @selector(context), block, OBJC_ASSOCIATION_COPY);}- (CDDContext *)context {    id (^block)() = objc_getAssociatedObject(self, @selector(context));    id currentContext = (block ? block() : nil);    return currentContext;}复制代码

KVO

Father

// .h#import 
    
     @interface Father : NSObject- (void)methodToBeInherit;@end// .m#import "Father.h"@implementation Father- (void)methodToBeInherit {    NSLog(@"Father Log");}@end复制代码

Son

// .h#import "Father.h"@interface Son : Father- (void)methodToBeInherit;@end// .m#import "Son.h"@implementation Son- (void)methodToBeInherit {//    [super methodToBeInherit];        struct objc_super superInfo = {        .receiver = self,        .super_class = class_getSuperclass(object_getClass(self))    };        void (*objc_msgSendSuperMethod)(void *, SEL) = (void *)objc_msgSendSuper;        objc_msgSendSuperMethod(&superInfo, _cmd);        NSLog(@"Son Log");}@end复制代码

Son *son = [[Son alloc] init];[son methodToBeInherit];复制代码

结果如下：

假如现在我们想要实现上述结果，但是不是用son，而是Father呢？如何实现？

// .h#import 
    
     @interface NSObject (Hook)- (void)isaSwizzingMethod;@end// .m#import "NSObject+Hook.h"#import "Son.h"#import 
     
      @implementation NSObject (Hook)- (void)isaSwizzingMethod {    Class newClass = [Son class];        object_setClass(self, newClass);}@end复制代码

Father *father = [[Father alloc] init];[father isaSwizzingMethod];    [father methodToBeInherit];复制代码

结果如下：

惊不惊喜，意不意外。

面向切面编程框架Aspects中有更多实现细节，感兴趣的可以去github下载demo一饱眼福。