NSSelector对象

用字符串来找方法:

SEL　变量名　=　NSSelectorFromString(方法名字的字符串);

运行中用SEL变量反向查出方法名字字符串:

NSString　*变量名　=　NSStringFromSelector(SEL参数);

SEL变量的执行:
[对象　performSelector:SEL变量　withObject:参数1　withObject:参数2];