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编译器会抱怨,除非显式引用了一个字典枚举键

types dictionary swift arrays

Besi · 技术社区 · 6 年前

我有以下枚举:

enum TaskKey: String{
    case title = "title"
    case completed = "completed"
    case children = "children"
}

现在我用这些键创建了一个字典:

    let taskDescriptions : Array<[TaskKey:Any]> = [
        [ .title : "Buy milk",
          .completed : false ],

        [ .title     : "Sleep",
          .completed : false,
          .children  :
            [
                // `TaskKey` is required here
                [ TaskKey.title     : "Find a bed",
                  .completed : false
                ],

                [ .title     : "Wait",
                  .completed : false
                ]
            ] ],

        [ .title     : "Dance",
          .completed : false ]
        ]

<[TaskKey:Any]> 我可以使用 .title 而不是 TaskKey.title . 然而,对于 .children TaskKey. 否则编译器会抱怨。

在我看来这有点奇怪。我假设编译器隐式地从 Any TaskKey:Any

我不知道我的假设是否正确。为了化妆品的缘故,也可以使用 .职务 语法也适用于我字典中的嵌套条目。

1 回复 | 直到 6 年前

vacawama 6 年前

[TaskKey:Any] 所以内部数组可以是任何类型。编译器需要一些关于 .title 是。一旦你把其中一个键用 TaskKey.title ,斯威夫特推断出其余的。

as [[TaskKey:Any]] 或同等地 as Array<[TaskKey:Any]>

let taskDescriptions : Array<[TaskKey:Any]> = [
    [ .title : "Buy milk",
      .completed : false ],

    [ .title     : "Sleep",
      .completed : false,
      .children  :
        [
            // `TaskKey` is required here
            [ .title     : "Find a bed",
              .completed : false
            ],

            [ .title     : "Wait",
              .completed : false
            ]
        ] as [[TaskKey:Any]] ],

    [ .title     : "Dance",
      .completed : false ]
]

注:

考虑使用 struct 或 class

我不确定字典是这里数据结构的最佳选择。你可以考虑使用 结构 或 :

class Task: CustomStringConvertible {
    var title: String
    var completed: Bool
    var children: [Task]
    var description: String { return "Task(title: \(title), completed: \(completed), children: \(children)" }  

    init(title: String, completed: Bool, children: [Task] = []) {
        self.title = title
        self.completed = completed
        self.children = children
    }
}

var taskDescriptions : [Task] = [
    Task(title: "Buy milk",
         completed: false
    ),

    Task(title: "Sleep",
      completed: false,
      children:
        [
            Task(title: "Find a bed",
              completed: false
            ),

            Task(title: "Wait",
              completed: false
            )
        ]
    ),

    Task(title: "Dance",
      completed: false
    )
]

这将比处理铸造要容易得多 Any 到所需类型。

使用这里(在一个房间里) 结构 )它使您能够轻松地更新内部任务:

例如:

// Mark all of the children tasks of the second task as completed
for task in taskDescriptions[1].children {
    task.completed = true
}