Swizzling UIButton example

+ (void)load {    static dispatch_once_t onceToken;    dispatch_once(&onceToken, ^{        Class class = [self class];                SEL originalSelector = @selector(_sendActionsForEvents: withEvent;        SEL swizzledSelector = @selector(fb_sendActionsForEvents: withEvent;                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)fb_sendActionsForEvents:(UIControlEvents)controlEvents withEvent:(UIEvent *)event {    if (controlEvents == UIControlEventTouchUpInside) {        DKFireBaseEventsManager *manager = [[DKFireBaseEventsManager alloc] init];        [manager logButtonAction:self.titleLabel.text];    }    [self fb_sendActionsForEvents:controlEvents withEvent:event];}