swift block。

B class中:

1. 然后typedef一下这个funcation:

typealias callbackfunc=(selectIndex:Int)->Void

2.var myFunc = callbackfunc?()

3.传递函数func initBack( mathFunction:(selectIndex:Int)->Void ){

myFunc = mathFunction

}

4.最后回调:

myFunc!(selectIndex: indexPath.row);

A class中写法:

xxx.initBack { (selectIndex) -> Void in

做点啥吧.

}