HOOK


+ (void)load
{
    SEL origSel = @selector(viewDidAppear:);
    SEL swizSel = @selector(swiz_viewDidAppear:);
    [UIViewController swizzleMethods:[self class] originalSelector:origSel swizzledSelector:swizSel];
}

+ (void)swizzleMethods:(Class)class originalSelector:(SEL)origSel swizzledSelector:(SEL)swizSel
{
    Method origMethod = class_getInstanceMethod(class, origSel);
    Method swizMethod = class_getInstanceMethod(class, swizSel);
     
    //class_addMethod will fail if original method already exists
    BOOL didAddMethod = class_addMethod(class, origSel, method_getImplementation(swizMethod), method_getTypeEncoding(swizMethod));
    if (didAddMethod) {
        class_replaceMethod(class, swizSel, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    } else {
        //origMethod and swizMethod already exist
        method_exchangeImplementations(origMethod, swizMethod);
    }
}

- (void)swiz_viewDidAppear:(BOOL)animated
{
    //此處注入程式碼
    //………..

   
    [self swiz_viewDidAppear:animated];
}