method_exchangeImplementations運行時動態改變兩個方法的實現 ~~~ /** ?* Exchanges the implementations of two methods. ?* ?* @param m1 Method to exchange with second method. ?* @param m2 Method to exchange with first method. ?* ?* @note This is an atomic version of the following: ?*? \code ?*? IMP imp1 = method_getImplementation(m1); ?*? IMP imp2 = method_getImplementation(m2); ?*? method_setImplementation(m1, imp2); ?*? method_setImplementation(m2, imp1); ?*? \endcode ?*/ OBJC_EXPORT void method_exchangeImplementations(Method m1, Method m2) ???? __OSX_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0); ~~~ 代碼： ~~~ - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. Method m1 = class_getInstanceMethod([self class], @selector(testExchange1)); Method m2 = class_getInstanceMethod([self class], @selector(testExchange2)); [self testExchange1]; [self testExchange2]; method_exchangeImplementations(m1, m2); [self testExchange1]; [self testExchange2]; } - (void) testExchange1 { NSLog(@"%s", __func__); } - (void) testExchange2 { NSLog(@"%s", __func__); } ~~~ 輸出： ~~~ 2015-11-02 13:38:40.264 02-runtime[2485:68367] -[ViewController testExchange1] 2015-11-02 13:38:40.266 02-runtime[2485:68367] -[ViewController testExchange2] 2015-11-02 13:38:40.281 02-runtime[2485:68367] -[ViewController testExchange2] 2015-11-02 13:38:40.281 02-runtime[2485:68367] -[ViewController testExchange1] ~~~ 通過代碼相信很容易理解吧