ios - 如何在 String Swift4 中交换两个字符？

Question

in Swift4, the String is Collections. You will no longer use characters property on a string.

func swapCharacters(input:String,index1:Int,index2:Int)-> String { // logic to swap }

let input = "ABCDEFGH"

如果我用 (input,3,8) 调用函数，那么输出应该是

输出: ABCHEFGD

注意:在 Swift4 中，字符串是集合。

Answer 1

相当简单，因为 String 是一个集合:

func swapCharacters(input: String, index1: Int, index2: Int) -> String {
    var characters = Array(input)
    characters.swapAt(index1, index2)

    return String(characters)
}

let input = "ABCDEFGH"
print(swapCharacters(input: input, index1: 3, index2: 7)) //ABCHEFGD

或者，提供一个直接的类似数组的操作:

extension String {
    mutating func swapAt(_ index1: Int, _ index2: Int) {
        var characters = Array(self)
        characters.swapAt(index1, index2)
        self = String(characters)
    }
}

var input = "ABCDEFGH"
input.swapAt(3, 7)
print(input) //ABCHEFGD