SEL

SEL就是對類中方法的包裝或者相當于C語言中的函數指針，同一個類中不能有同名函數，即使參數類型不同也不行，因為SEL就是根據函數名而确定的

SEL定義：

/// An opaque type that represents a method selector.
typedef struct objc_selector *SEL;
           

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    SEL selTest = @selector(test);
    
    SEL selTest1 = NSSelectorFromString(@"test");
    
    [self performSelector:selTest withObject:nil];
    
    [self performSelector:selTest1 withObject:nil];
    
    NSString * selTestStr = NSStringFromSelector(selTest);
    
    NSLog(@"%@", selTestStr);
    
    SEL test1 = @selector(test1:);
    
    SEL test11 = NSSelectorFromString(@"test1:");
    
    [self performSelector:test1 withObject:@"params"];
    
    [self performSelector:test11 withObject:@"params"];
    
    
    SEL test2 = @selector(test:withStr:);
    
    [self performSelector:test2 withObject:@"s1" withObject:@"s2"];
    
}

- (void) test{
    NSLog(@"test-------");
}
- (void) test:(NSString *) str withStr:(NSString *) str2{
    NSLog(@"test2--%@--%@", str, str2);
}
- (void) test1:(NSString *) str {
    NSLog(@"test1--%@", str);
}
           

輸出：

2015-11-02 13:16:42.856 02-runtime[2384:64080] test-------
2015-11-02 13:16:42.857 02-runtime[2384:64080] test-------
2015-11-02 13:16:42.859 02-runtime[2384:64080] test
2015-11-02 13:16:42.861 02-runtime[2384:64080] test1--params
2015-11-02 13:16:42.861 02-runtime[2384:64080] test1--params
2015-11-02 13:16:42.862 02-runtime[2384:64080] test2--s1--s2
           

好像最多隻有兩個參數的，沒有performSelector:參數 withObject:參數 withObject:參數 withObject:參數   這樣的函數