Swift 如何循环到数组中并切换到其索引

我有以下数组：

let dict = [("Steve", 17),
             ("Marc", 38),
             ("Xavier", 21),
             ("Rolf", 45),
             ("Peter", 67),
             ("Nassim", 87),
             ("Raj", 266),
             ("Paul", 220),
             ("Bill", 392)]

如何循环并切换到索引，以便在前三个、后三个和后三个中进行操作。

您可以通过where子句指定索引的步骤：

for index in 0..<dict.count where index % 3 == 0 {
    // here you can do action with index, index + 1, index + 2 items in way you need
}

您可以使用dict.enumerated获取idx项元组序列，然后for可以通过该序列进行枚举。例如：

let dict = [("Steve", 17),
            ("Marc", 38),
            ("Xavier", 21),
            ("Rolf", 45),
            ("Peter", 67),
            ("Nassim", 87),
            ("Raj", 266),
            ("Paul", 220),
            ("Bill", 392)]

for (idx, item) in dict.enumerated() {
    let (name, value) = item

    switch (idx / 3) {
    case 0:
        print("\(name) is in the first group")
    case 1:
        print("\(name) is in the second group")
    case 2:
        print("\(name) is in the third group")
    default:
        print("\(name) not in first 3 groups")
    }

    print("value is \(value)")
}

输出：

Players: Steve, Marc, Xavier
Result: 199
Result: 878

或者等效地，您可以直接打开它，而不是基于索引进行整数计算，但使用一个范围来处理以下情况：

switch idx {
case 0...2:
    print("\(name) is in the first group")
case 3...5:
    print("\(name) is in the second group")
case 6...8:
    print("\(name) is in the third group")
default:
    print("\(name) not in first 3 groups")
}

---

您可以使用数组扩展按给定大小的块拆分数组：

extension Array {

    func chunked(by distance: IndexDistance) -> [[Element]] {
        return stride(from: startIndex, to: endIndex, by: distance).map {
            let newIndex = index($0, offsetBy: distance, limitedBy: endIndex) ?? endIndex
            return Array(self[$0 ..< newIndex])
        }
    }
}

输出：

Players: Steve, Marc, Xavier
Result: 199
Result: 878

---

请不要在标题中添加标签，尤其不要无故在标题中使用特殊字符。这使得将来有类似问题的人更难找到你的问题。将元组数组命名为dict是非常误导的。

Players: Steve, Marc, Xavier
Result: 199
Result: 878