如何在 Swift 中遍历字典的特定部分？

Question

我引入了一些 JSON，将其转换为字典，并想知道是否有有效的方法来迭代它的特定级别（嵌套是什么）

例如，从以下开始：

{
    "instrument": {
        "piano": {
            "sounds": {
                "C": "pianoC.mp3",
                "D": "pianoD.mp3",
                "E": "pianoE.mp3",
                "F": "pianoF.mp3",
                "G": "pianoG.mp3",
                "A": "pianoA.mp3",
                "B": "pianoB.mp3",
                "C8": "pianoC8.mp3"
             }
         },
         "guitar": {
             "sounds": {
                 "CMajor": "guitarCMajor.mp3”,
                 "FMajor": "guitarDMajor.mp3",
                 "GMajor": "guitarGMajor.mp3",
                 "AMinor": "guitarAMinor.mp3"
             }
         }
    }
}

你将如何迭代声音？

Answer 1

我给Dictionary写了一些扩展：

extension Dictionary {
    func filterValues<T>() -> [T] {
        return values.filter { $0 is T }.map { $0 as! T }
    }

    func filterDictionaries() -> [Dictionary] {
        return filterValues()
    }

    func valuesOfLevel<T>(level: Int) -> [T] {
        var levelItems = [self]
        for _ in 0..<level-1 {
            levelItems = levelItems.flatMap { $0.filterDictionaries() }
        }
        return levelItems.flatMap { $0.filterValues() }
    }

    func dictionariesOfLevel(level: Int) -> [Dictionary] {
        return valuesOfLevel(level)
    }

    func dictionariesOfLevel(level: Int, key: Key) -> [Dictionary] {
        return dictionariesOfLevel(level)
            .flatMap { ($0[key] as? Dictionary) ?? [:] }
            .filter { !$0.isEmpty }
    }

    func valuesOfLevel<T>(level: Int, key: Key) -> [T] {
        return dictionariesOfLevel(level, key: key)
            .flatMap { $0.values }
            .filter { $0 is T }
            .map { $0 as! T }
    }
}

在您的情况下，您可以过滤声音并通过以下方式遍历它们：

let sounds: [String] = dictionary.valuesOfLevel(2, key: "sounds")

for sound in sounds {
  // ...
}