ios - 使 Collection 符合自定义协议(protocol)

Question

我想为所有具有 isEmpty 的集合类型添加一个通用参数，这样当我尝试创建 Collection 时，它们也可以具有 isNotEmpty符合Occupiable我得到一个编译错误

error here : Extension of protocol 'Collection' cannot have an inheritance clause

String 也符合 Array 固有的协议(protocol)，因此一旦我们找到上述问题的解决方案，我们是否可以删除 extension String: Occupiable { } ？

// Anything that can hold a value (strings, arrays, etc)
protocol Occupiable {
    var isEmpty: Bool { get }
    var isNotEmpty: Bool { get }
}

// Give a default implementation of isNotEmpty, so conformance only requires one implementation
extension Occupiable {
    var isNotEmpty: Bool {
        return !isEmpty
    }
}

extension String: Occupiable { }

//  error here : Extension of protocol 'Collection' 
//  cannot have an inheritance clause
extension Collection: Occupiable { }

Answer 1

您需要设置一致性约束。这将修复该错误。

extension Collection where Self: Occupiable { }