ios - Swift 4 按第一个值排序字典

Question

我正在使用 Swift 4 开发一个 iOS 应用程序，我有一个这样的字典:

var list = [
"US" : ["United-States","$"], 
"FR" : ["France","€"],
"CN" :["China", "¥"]
]

我想根据每个键的第一个值对基于此字典的 UITableView 进行排序，以获得以下结果:

China
France
United-States

这这可能吗？

Answer 1

您可以获得字典值(数组)，映射它们的第一个元素并对其进行排序:

let list = ["US" : ["United-States","$"],
            "FR" : ["France","€"],
            "CN" : ["China", "¥"]]

let countries = list.values.compactMap{$0.first}.sorted()

print(countries)    // ["China", "France", "United-States"]

---

另一种选择是为您的货币创建一个结构，创建一个采用键值对并使其符合 Comparable 协议(protocol)的自定义初始化程序:

struct Currency: CustomStringConvertible, Comparable {
    let name: String
    let code: String
    let symbol: String
    init?(currency: (key: String, value: [String])) {
        guard currency.value.count == 2 else { return nil }
        self.code = currency.key
        self.name = currency.value.first!
        self.symbol = currency.value.last!
    }

    var description: String {
        return "Code: \(code)\nName: \(name)\nSynmbol: \(symbol)\n"
    }
}
extension Currency {
    static func <(lhs: Currency, rhs: Currency) -> Bool {
        return lhs.name < rhs.name
    }
}

---

let list = ["US" : ["United-States","$"],
            "FR" : ["France","€"],
            "CN" :["China", "¥"]]

let currencies = list.compactMap(Currency.init).sorted()
currencies.map({print($0)})

这将打印:

Code: CN

Name: China

Synmbol: ¥

Code: FR

Name: France

Synmbol: €

Code: US

Name: United-States

Synmbol: $