ios - Swift:字符后的字符串firstIndex

Question

我正在尝试检测字符串上的括号，例如: foo(bar)baz(blim) 并反转括号内的内容，但我超出了反弹范围我的实现:

func reverseInParentheses(inputString: String) -> String {
    var tmpStr = inputString
    var done = false
    while !done {
        if let lastIndexOfChar = tmpStr.lastIndex(of: "(") {
            let startIndex = tmpStr.index(lastIndexOfChar, offsetBy:1)
            if let index = tmpStr.firstIndex(of: ")") {
                let range = startIndex..<index
                let strToVerse = String(tmpStr[range])
                let reversedStr = reverseStr(str: strToVerse)
                tmpStr = tmpStr.replacingOccurrences(of: "(" + strToVerse + ")", with: reversedStr)
                
            }
        } else {
            done = true
        }
    }
    return tmpStr
}

如何在 startIndex 之后获取 tmpStr.firstIndex(of: ")") 你们知道如何做到这一点吗？

Answer 1

how can I get the tmpStr.firstIndex(of: ")") after the startIndex?

一种方法是在 startIndex 处“剪切”字符串，并获取后半部分。然后在子字符串上使用 firstIndex(of:) 。由于 Substring 只是从中剪切它们的原始字符串的“ View ”，因此 firstIndexOf 仍然返回原始字符串的索引。

let string = "foo(bar)baz(blim)"
if let lastIndexOfChar = string.lastIndex(of: "(") {
    let startIndex = string.index(after: lastIndexOfChar)
    let substring = string[startIndex..<string.endIndex] // cut off the first part of the string.
    // now you have a "Substring" object
    if let indexAfterOpenBracket = substring.firstIndex(of: ")") {
        // prints "blim", showing that the index is indeed from the original string
        print(string[startIndex..<indexAfterOpenBracket])
    }
}

您可以将其编写为扩展:

extension StringProtocol {
    func firstIndex(of char: Character, after index: Index) -> Index? {
        let substring = self[index..<endIndex]
        return substring.firstIndex(of: char)
    }
}

现在，如果您在 reverseInParentheses 中调用 tmpStr.firstIndex(of: ")", after: startIndex)，它应该可以工作。