Runtime应用之交换方法实现

Runtime一个常用的场景是交换方法的调用。其实就是利用了Runtime的方法交换，具体代码如下：

- (void)viewDidLoad {
    [super viewDidLoad];
    [self doExchange];
    [ViewController doPrint1];
    // Do any additional setup after loading the view.
}

-(void)doExchange{
    Method originalMethod = class_getInstanceMethod([self class], @selector(doPrint1));
    Method swizzledMethod = class_getInstanceMethod([self class], @selector(doPrint2));
    
    method_exchangeImplementations(originalMethod, swizzledMethod);
}
+(void)doPrint1{
    NSLog(@"print-----------");
}
+(void)doPrint2{
    NSLog(@"print+++++++++++");
}

核心思路是先找到对应的Method，然后将其交换就OK。
上面实现的是交换实例方法，如果交换类方法的话，会发现Method是nil，这是因为类方法是存储在类所对应的源类的，代码需要修改一下：

- (void)viewDidLoad {
    [super viewDidLoad];
    [self doExchange];
    [ViewController doPrint1];
    // Do any additional setup after loading the view.
}

-(void)doExchange{
    Method originalMethod = class_getInstanceMethod(objc_getMetaClass("ViewController"), @selector(doPrint1));
    Method swizzledMethod = class_getInstanceMethod(objc_getMetaClass("ViewController"), @selector(doPrint2));
    
    method_exchangeImplementations(originalMethod, swizzledMethod);
}
+(void)doPrint1{
    NSLog(@"print-----------");
}
+(void)doPrint2{
    NSLog(@"print+++++++++++");
}

核心还是先找到对应的Method，只不过类方法需要去到源类里面寻找，然后将其对应交换就OK。

我曾执笔雕刻时光 奈何良辰难书过往