Swift - How to split an string i

最近一个朋友问了我一个问题，怎么将005056b12cda变成00:50:56:b1:2c:da

规律：按照一定的长度逐步分割字符串，并用特定的分割符将这些小段的字符串连成一个新的字符串

1.stride(from:to:by:)官方文档

//Returns a sequence from a starting value to, but not including, an end value, stepping by the specified amount.
func stride<T>(from start: T, to end: T, by stride: T.Stride) -> StrideTo<T>where T : Strideable

You can use this function to stride over values of any type that conforms to the Strideable protocol, such as integers or floating-point types. Starting with start, each successive value of the sequence adds stride until the next value would be equal to or beyond end.

你可以使用此函数跨过遵循Strideable协议的任何类型的值，例如整数或浮点类型。从start开始，序列的每个连续值都会增加步幅，直到下一个值等于或超过end

2.可是String类型没有遵循Strideable协议，不能直接进行stride操作，但是Array遵循该协议，而正好String也是集合类型，我们可以先将字符串转成Array，进行stride后遍历的到的序列，再将元素拼接成我们想要的字符串：

//swift 4.0+

extension Array {
    func chunked(into size: Int) -> [[Element]] {
        return stride(from: 0, to: count, by: size).map {
            Array(self[$0 ..< Swift.min($0 + size, count)])
        }
    }
}

extension String {
    func chunked(into size: Int, separatedBy separator: String) -> String {
        let array = Array(self)
        let newArray = array.chunked(into: size)
        var newString = ""
        for (index, item) in newArray.enumerated() {
            if index == 0 {
                newString = String(item)
            } else {
                newString += separator + String(item)
            }
        }
        return newString
    }
}

let str = "005056b12cda"
str.chunked(into: 2, separatedBy: ":")

Playground运行结果

参考：

• How to split an array into chunks