ios - 在快速给出错误时初始化字典数组

Question

我在 swift 中遇到了奇怪的行为。我有

let valueOne: [String: String] = [
    "title": "May 29th",
    "value": "260"
]

let valueTwo = [
    "title": "April 24th",
    "value": "260"
]

var historyData = [valueOne, valueTwo]

但这给了我一个编译器错误

xxxController.type does not have a member named 'valueOne'

当我尝试的时候

let valueOne: [String: String] = [
    "title": "May 29th",
    "value": "260"
]

let valueTwo = [
    "title": "April 24th",
    "value": "260"
]

var historyData = [
    [
        "title": "May 29th",
        "value": "260"
    ],
    [
        "title": "April 24th",
        "value": "260"
    ]
]

它工作正常没有错误。此外，当我在 Playground 中尝试这两种代码时，它们都工作正常。

我的问题是我在第一个片段中做错了什么？

Answer 1

假设你这样做:

class xxxController: UIViewController {

    let valueOne: [String: String] = [
        "title": "May 29th",
        "value": "260"
    ]

    let valueTwo = [
        "title": "April 24th",
        "value": "260"
    ]

    var historyData = [valueOne, valueTwo]

    // ....
}

你不能这样做，因为我们不能在 class 声明中引用 instance 属性。

相反，在这种情况下，您应该使它们成为static 属性:

class xxxController: UIViewController {

    static let valueOne: [String: String] = [
        "title": "May 29th",
        "value": "260"
    ]

    static let valueTwo = [
        "title": "April 24th",
        "value": "260"
    ]

    var historyData = [valueOne, valueTwo]

    // ....
}

或者在初始化器中初始化historyData:

class xxxController: UIViewController {

    let valueOne: [String: String] = [
        "title": "May 29th",
        "value": "260"
    ]

    let valueTwo = [
        "title": "April 24th",
        "value": "260"
    ]

    var historyData:[[String: String]]

    required init(coder aDecoder: NSCoder) {
        historyData = [valueOne, valueTwo]
        super.init(coder: aDecoder)
    }

    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
        historyData = [valueOne, valueTwo]
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    }

    // ....
}

或将 historyData 设为 [[String: String]]! 并在 viewDidLoad() 中分配给它:

class xxxController: UIViewController {

    let valueOne: [String: String] = [
        "title": "May 29th",
        "value": "260"
    ]

    let valueTwo = [
        "title": "April 24th",
        "value": "260"
    ]

    var historyData:[[String: String]]!

    override func viewDidLoad() {
        super.viewDidLoad()
        historyData = [valueOne, valueTwo]
    }

    // ....
}