string - 交换字符串大小写 - swift

Question

let str = "tHIS is A test"
let swapped_case = "This IS a TEST"

这里是 Swift 菜鸟，如何以编程方式执行第二条语句？

Answer 1

此函数适用于所有大写/小写字符以 Unicode 定义，甚至是来自“外国”语言(例如 Ä 或 ć)的那些:

func swapCases(_ str : String) -> String {
    var result = ""
    for c in str.characters { // Swift 1: for c in str {
        let s = String(c)
        let lo = s.lowercased() //Swift 1 & 2: s.lowercaseString
        let up = s.uppercased() //Swift 1 & 2: s.uppercaseString
        result += (s == lo) ? up : lo
    }
    return result
}

例子:

let str = "tHIS is a test ÄöÜ ĂćŒ Α" // The last character is a capital Greek Alpha
let swapped_case = swapCases(str)
print(swapped_case)
// This IS A TEST äÖü ăĆœ α