"黑魔法"Method Swizzling和IMP指针

typedef void (*_VIMP)(id, SEL, ...);

@implementation UIViewController (category)

+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
//        获取原始方法
Method viewWillAppear = class_getInstanceMethod(self, @selector(viewWillAppear:));
//        获取方法的实现
_VIMP viewWillAppear_IMP = (_VIMP)method_getImplementation(viewWillAppear);
//        重新设置方法实现
method_setImplementation(viewWillAppear, imp_implementationWithBlock(^(id target){
//            调用原有方法
viewWillAppear_IMP(target,@selector(viewWillAppear:));
[MobClick beginLogPageView:NSStringFromClass([target class])];
}));
//TODO...可以自己添加viewWillDisappear等等
});
}

@end

@implementation UIViewController (category)

+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [self class];
// When swizzling a class method, use the following:
// Class class = object_getClass((id)self);
swizzleMethod(class, @selector(viewDidLoad), @selector(aop_viewDidLoad));
swizzleMethod(class, @selector(viewDidAppear:), @selector(aop_viewDidAppear:));
swizzleMethod(class, @selector(viewWillAppear:), @selector(aop_viewWillAppear:));
swizzleMethod(class, @selector(viewWillDisappear:), @selector(aop_viewWillDisappear:));
});
}
void swizzleMethod(Class class, SEL originalSelector, SEL swizzledSelector)   {
Method originalMethod = class_getInstanceMethod(class, originalSelector);
Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
BOOL didAddMethod =
class_addMethod(class,
originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(class,
swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}

- (void)aop_viewDidAppear:(BOOL)animated {
[self aop_viewDidAppear:animated];
}

-(void)aop_viewWillAppear:(BOOL)animated {
[self aop_viewWillAppear:animated];
#ifndef DEBUG
[MobClick beginLogPageView:NSStringFromClass([self class])];
#endif
}

-(void)aop_viewWillDisappear:(BOOL)animated {
[self aop_viewWillDisappear:animated];
#ifndef DEBUG
[MobClick endLogPageView:NSStringFromClass([self class])];
#endif
}

- (void)aop_viewDidLoad {
[self aop_viewDidLoad];
}

@end