斯威夫特 – ‘[任务]？不可转换为’Optional <[Any]>'

我做了扩展

extension Optional where Wrapped == [Any] {
   var isNilOrEmpty: Bool {
       get {
           if let array = self {
              return array.count == 0
           } else {
            return false
           }
       }
    }
}

然后我尝试像这样使用它

if fetchedResults.fetchedobjects.isNilOrEmpty { ... }

我收到了错误

‘[Task]?’ is not convertible to ‘Optional<[Any]>’

但是,按照规范

Any can represent an instance of any type at all,including function types.

这里我的错误是什么？
如果重要的话,Task是NSManagedobject的子类.

解决方法

好吧,[Task]和[Any]是两种不同的类型,Wrapped == [Any]不起作用.

正确的方法是限制Wrapped by protocol,而不是特定的类型.

extension Optional where Wrapped: Collection {
    var isNilOrEmpty: Bool {
        get { // `get` can be omitted here,btw
            if let collection = self {
                return collection.isEmpty // Prefer `isEmpty` over `.count == 0`
            } else {
                return true // If it's `nil` it should return `true` too
            }
        }
    }
}