ObjC中_cmd的用法

look_w

1.直接代码展示

    (void)viewDidLoad
    {
    [super viewDidLoad];
        NSLog(@"%@ call",NSStringFromSelector(_cmd));
    }
     
    输出结果如下：
    2018-05-17 10:33:35.583110+0800 CoreGraphicsDemo_Example[99368:13538878] viewDidLoad call

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image.png

_cmd在Objective-C的方法中表示当前方法的selector，正如同self表示当前方法调用的对象实例。

    //比如需要打印当前被调用的方法，可以在一个方法中添加：
    NSLog(@"%@ call",NSStringFromSelector(_cmd));
    //会输出类似
    //2013-01-10 11:25:46.902 TDDataViewer[855:303] applicationDidFinishLaunching: call
    //这样的内容。
     
    //在cocos2d中，_cmd通常用于定时调用某个函数（schedule）
    //比如下面方法利用_cmd能够不定时地调用某个函数
    -(void) scheduleUpdates {
        // schedule the first update as usual
        [self scheduleselector(irregularUpdate interval:1];
    }
    -(void) irregularUpdateccTime)delta {
        // unschedule the method first [self unschedule:_cmd];
        // I assume you’d have some kind of logic other than random to determine
        // the next time the method should be called
        float nextUpdate = CCRANDOM_0_1() * 10;
        // then re-schedule it with the new interval using _cmd as the selector
        [self schedule:_cmd interval:nextUpdate];
    }
     

2.其他用法：

    - (CustomNavigationControllerDelegate *)customDelegate
    {
        return objc_getAssociatedObject(self, _cmd);
    }
     
    - (void)setCustomDelegateCustomNavigationControllerDelegate *)customDelegate
    {
        objc_setAssociatedObject(self, @selector(customDelegate), customDelegate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }