为什么只有类的协议不满足协议扩展where子句中的AnyObject约束？

I defined protocol:

我定义了协议：

protocol MyProtocol: class {   
}

class MyClass: MyProtocol {
}

And extension only for collections with class elements:

并且只对具有类元素的集合进行扩展：

extension CollectionType where Generator.Element: class {
    func someFunc() {
    }
}

var items = [MyClass]()
items.someFunc() // someFunc is available

var strings = [String]()
// strings.someFunc() is not available because String is not class

But this does not compile and I changed extension definition to:

但这不编译，我将扩展定义更改为：

extension CollectionType where Generator.Element: AnyObject {
...
}

It also does not compile because MyProtocol does not conform to AnyObject. So I changed definition of MyProtocol to:

它也不会编译，因为MyProtocol不符合AnyObject。所以我将MyProtocol的定义更改为：

protocol MyProtocol: AnyObject {   
}

It also does not compile with message:

它也不会与消息编译：

Type 'MyProtocol' does not conform to protocol 'AnyObject'.

类型'MyProtocol'不符合协议'AnyObject'。

1 个解决方案

#1

After a little research I found here that protocol type can not conform to protocol:

经过一番研究后我发现协议类型不符合协议：

extension CollectionType where Generator.Element : First {
    func someFunc() {
    }
}

protocol First {

}

protocol Second: First {
}

var items = [Second]()

items.someFunc() // Type 'Second' does not conform to protocol 'First'

So the real issue in my case is not that class-only protocol does not satisfy AnyObject constraint but that protocol type can not conform AnyObject protocol or any other protocol.

因此，在我的情况下，真正的问题不是仅类协议不满足AnyObject约束，而是协议类型不能符合AnyObject协议或任何其他协议。

#1