Object-C-selector

Shape *shape=[[Shape alloc]init];

//[shape draw]

SEL selDraw=@selector(draw);

[shape performSelector:selDraw];

[shape performSelector:@selector(draw:)withObject:@"red"];

[shape performSelector:@selector(draw:andType:)withObject:@"yellow" withObject:@"circle"];

respondsToSelector:

if([shape respondsToSelector:@selector(draw)])判断时候存在这个方法

NSStringFromSelector:

NSLog(@"%@",NSStringFromSelector(selraw))//打印 draw

好处作为函数指针，方便消息传递

Cocoa 中很多系统采用@selector进行参数传递