swift - 如何使用符合某些协议(protocol)的属性声明一个 swift 类

Question

swift 有可能有一个 ViewController 吗？从 xib 初始化的类有一个属性也是 UIViewController 的子类并符合某些协议(protocol)？

    protocol SomeProtocol {
        // Some methods
    }

    class ViewController: UIViewController {
        // contentView is initialized from xib
        @IBOutlet weak var contentView: UIView!

        // I'd like to declare anotherViewController both conforms to 'SomeProtocol' 
        // and a subclass of UIViewController
        var anotherViewController: UIViewController!
        ...
    }  

当我声明ViewController作为通用类，说 class ViewController<T: UIViewController, SomeProtocol> ，我得到一个错误:

"Variable in a generic class cannot be presented in Objective-C"

那么如果不能使用泛型类怎么实现呢？

Answer 1

如果我误解了你的问题，请原谅我，但我认为你想要做的是声明一个继承自 UIViewController 并符合 SomeProtocol 的新类型，如下所示:

protocol SomeProtocol { }

class VCWithSomeProtocol: UIViewController, SomeProtocol {

}

class ViewController: UIViewController {
    var anotherViewController: VCWithSomeProtocol!
}