Swift:符合特定类并同时符合多个协议的属性 [英] Swift: Property conforming to a specific class and in the same time to multiple protocols

问题描述

在 Objective-C 中，可以这样写:

In Objective-C, it's possible to write something like that:

@property(retain) UIView<Protocol1, Protocol2, ...> *myView;

但是我如何快速编写这段代码?

But how can I write this code in swift?

我已经知道如何使一个属性符合许多协议，但它不能通过使用继承来工作:

I already know how to make a property conform to many protocols, but it does not work by using the inheritance:

var myView: ??? protocol<Protocol1, Protocol2, ...>

我使用了很多 UIView 子类型，比如 UIImageView、UILabel 或其他，我需要使用一些 UIViewcode> properties 加上协议中定义的一些方法.在最坏的情况下，我可以使用所需的属性创建一个 UIViewProtocol，但我想知道是否可以在 Swift 中声明具有类型和一些协议的属性/变量.

I use many UIView subtypes like UIImageView, UILabel or others, and I need to use some of the UIView properties plus some methods defined in the protocols. In the worst case I could create a UIViewProtocol with the needed properties, but I would know if it is possible in Swift to declare a property/variable with a type and some protocol to conform with.

推荐答案

您可以使用 where 子句:

where 子句使您能够要求关联类型符合到某个协议，和/或某些类型参数和关联类型相同.

A where clause enables you to require that an associated type conforms to a certain protocol, and/or that certain type parameters and associated types be the same.

要使用它，请使用 输入约束以检查类型参数与您想要的基类匹配和协议.

To use it, make the class your property is defined in a generic class with a type constraint to check if the type parameter for your property matches your desired base class and protocols.

对于您的具体示例，它可能如下所示:

For your specific example, it could look something like this:

class MyViewController<T where T: UIView, T: Protocol1, T: Protocol2>: UIViewController {
    var myView: T

    // ...
}

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