swift - 如何转换为类中的协议(protocol)类型？

Question

这是我的代码:

protocol ProtocolA {
    static var myProperty: Int { get }
}

protocol ProtocolB {}

extension ProtocolB {
    func letsDoSomething() {
        (Self.self as! ProtocolA.Type).myProperty // Works
    }
}

class MyClass {
    func castSelfToProtocolAType() {
        (Self.self as! ProtocolA.Type).myProperty // Doesn't work
        (Self as! ProtocolA.Type).myProperty // Doesn't work also
    }
}

如何将 MyClass 中的 self 转换为动态类型(如在协议(protocol)扩展中)ProtocolA.Type？

Answer 1

根据您的问题，您正在尝试将您的类实例转换为协议(protocol)类型实例，这是不可能的，因为您的类不符合该协议(protocol)。

The direct casting from class/struct instance to protocol type instance is not possible, you can only convert to protocol type by accepting that class/struct as a method parameter or by assigning to the other property which protocol type, this is known as implicit type casting.

请阅读本文以了解有关协议(protocol)和类类型的更多信息

1. https://medium.com/swift-india/protocol-the-power-of-swift-5dfe9bc41a99
2. https://medium.com/swift-india/protocol-the-power-of-swift-950c85bb69b1
3. https://medium.com/swift-india/protocol-the-power-of-swift-45e97f6531f9
4. https://medium.com/@hitendrahckr/protocol-the-power-of-swift-6906cdedd867
5. https://medium.com/swift-india/protocol-the-power-of-swift-1e5b86bfd1dc