切片字符串 Swift

Question

我想将一个很长的字符串从一个词分割成另一个词。我想得到这些词之间的子串。为此，我使用以下字符串扩展名：

 extension String {
 func slice(from: String, to: String) -> String? {

 guard let rangeFrom = range(of: from)?.upperBound else { return nil }

 guard let rangeTo = self[rangeFrom...].range(of: to)?.lowerBound else { return nil }

 return String(self[rangeFrom..<rangeTo])
 }

效果非常好，但我的原始字符串包含一些 "from" "to"-words 我需要这两个词之间的每个子字符串，但是我的扩展我只能得到第一个子串。

示例：

let raw = "id:244476end36475677id:383848448end334566777788id:55678900end543"

我想从此原始字符串示例中获取以下子字符串：

sub1 = "244476"
sub2 = "383848448"
sub3 = "55678900"

如果我打电话：

var text = raw.slice(from: "id:" , to: "end")

我只得到第一次出现 (text = "244476")

感谢您的阅读。每个答案都会很好。

PS：我在 Whosebug 中制作代码片段时总是出错。

Answer 1

与其尝试从头到尾解析字符串，不如结合使用现有方法将其转换为所需结果。以下是我将如何做到这一点：

import Foundation

let raw = "id:244476end36475677id:383848448end334566777788id:55678900end543"

let result = raw
    .components(separatedBy: "id:")
    .filter{ ![=10=].isEmpty }
    .map { segment -> String in
        let slices = segment.components(separatedBy: "end")
        return slices.first! // Removes the `end` and everything thereafter
    }

print(result) // => ["244476", "383848448", "55678900"]

Answer 2

您可以使用 while 循环重复从该点到字符串末尾的搜索并使用 map 从结果范围中获取子字符串：

extension StringProtocol {
    func ranges<S:StringProtocol,T:StringProtocol>(between start: S, and end: T, options: String.CompareOptions = []) -> [Range<Index>] {
        var ranges: [Range<Index>] = []
        var startIndex = self.startIndex
        while startIndex < endIndex,
            let lower = self[startIndex...].range(of: start, options: options)?.upperBound,
            let range = self[lower...].range(of: end, options: options) {
            let upper = range.lowerBound
            ranges.append(lower..<upper)
            startIndex = range.upperBound
        }
        return ranges
    }
    func substrings<S:StringProtocol,T:StringProtocol>(between start: S, and end: T, options: String.CompareOptions = []) -> [SubSequence] {
        ranges(between: start, and: end, options: options).map{self[[=10=]]}
    }
}

游乐场测试：

let string = """
your text
id:244476end
id:383848448end
id:55678900end
the end
"""

let substrings = string.substrings(between: "id:", and: "end")  // ["244476", "383848448", "55678900"]

切片字符串 Swift

Slicing Strings Swift

iphone

xcode

ios

swift

ios13