objective-c - iOS Swizzle 方法出现问题.-PHP中文网问答

我通过以下方式hook方法,

static IMP _original_viewWillAppear;
void _swizzle_viewWillAppear(id self, SEL _cmd, BOOL animated) {
    NSDate *start = [NSDate date];
    
    void (*ori_imp)(id, SEL, BOOL) = (void(*)(id, SEL, BOOL))_original_viewWillAppear;
    ori_imp(self, _cmd, animated);
    
    NSDate *end = [NSDate date];
    NSTimeInterval elapsed = [end timeIntervalSinceDate:start];
    
    NSLog(@"Elapsed:%f(s)",elapsed);
}

@implementation UIViewControllerTrace

+ (void)startTrace {
    Method ori = class_getInstanceMethod([UIViewController class], @selector(viewDidLoad));
    _original_viewDidLoad = method_setImplementation(ori, (IMP)_swizzle_ViewDidLoad);
    
    ori = class_getInstanceMethod([UIViewController class], @selector(viewWillAppear:));
    _original_viewWillAppear = method_setImplementation(ori, (IMP)_swizzle_viewWillAppear);
}

ViewController的方法:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    sleep(2);
}

我在viewWillAppear sleep多少, hook方法的log都是错误的.

请问为什么会这样?

NSDate *start = [NSDate date]; NSLog(@"%@start%@",self,start); void (*ori_imp)(id, SEL, BOOL) = (void(*)(id, SEL, BOOL))_original_viewWillAppear; ori_imp(self, _cmd, animated); //可以试着替换下方法就可以了例如切换到viewDidAppear中 sleep // IMP imp = class_getMethodImplementation([self class], @selector(viewDidAppear:)); // void (*ori_imp)(id, SEL, BOOL) = (void(*)(id, SEL, BOOL))imp; // ori_imp(self, _cmd, animated); NSDate *end = [NSDate date]; NSLog(@"%@end%@",self,end); NSTimeInterval elapsed = [end timeIntervalSinceDate:start]; NSLog(@"Elapsed:%f(s)",elapsed);