无法将不可变值作为[Character]参数类型为swift的inout值传递

Question

我编写了以下方法，并尝试调用和运行该方法，但是我在geeting不能将不变值作为inout错误传递。

func compress(_ chars: inout [Character]) -> Int {

    var index = 0, currentCount = 0

    for i in 0..<chars.count
    {
        currentCount += 1

        if i+1 == chars.count || chars[i] != chars[i+1]
        {
            chars[index] = chars[i]
            if currentCount != 1
            {
                chars.replaceSubrange(index + 1...String(currentCount).count + index, with : Array(String(currentCount)))

            }

            index += currentCount == 1 ? 1 : 1 + String(currentCount).count
            currentCount = 0

        }
    }

  return index
}

print(compress(["a","a","b","b","c","c","c"]))

  

不能将不可变值作为[Character]类型的inout值传递   争论迅速