使用 Swift，你如何在 Python 中像这个短脚本一样重新编码然后解码一个字符串？

Question

XKCD 的 API 存在一些问题和奇怪的编码问题。

Minor encoding issue with xkcd alt texts in chat

解决方案（在 Python 中）是将其编码为 latin1，然后解码为 utf8，但如何在 Swift 中做到这一点？

测试字符串：

"Be careful\u00e2\u0080\u0094it's breeding season"

预期输出：

Be careful—it's breeding season

Python（来自上面的链接）：

import json
a = '''"Be careful\u00e2\u0080\u0094it's breeding season"'''
print(json.loads(a).encode('latin1').decode('utf8'))

这是如何在 Swift 中完成的？

let strdata = "Be careful\\u00e2\\u0080\\u0094it's breeding season".data(using: .isoLatin1)!
let str = String(data: strdata, encoding: .utf8)

这行不通！

Answer 1

您必须先解码 JSON 数据，然后提取字符串，最后“修复”字符串。这是一个自包含的示例，其中包含来自https://xkcd.com/1814/info.0.json 的 JSON：

let data = """
    {"month": "3", "num": 1814, "link": "", "year": "2017", "news": "",
    "safe_title": "Color Pattern", "transcript": "",
    "alt": "\\u00e2\\u0099\\u00ab When the spacing is tight / And the difference is slight / That's a moir\\u00c3\\u00a9 \\u00e2\\u0099\\u00ab",
    "img": "https://imgs.xkcd.com/comics/color_pattern.png",
    "title": "Color Pattern", "day": "22"}
""".data(using: .utf8)!

// Alternatively:
// let url = URL(string: "https://xkcd.com/1814/info.0.json")!
// let data = try! Data(contentsOf: url)

do {
    if let dict = (try JSONSerialization.jsonObject(with: data, options: [])) as? [String: Any],
        var alt = dict["alt"] as? String {

        // Now try fix the "alt" string
        if let isoData = alt.data(using: .isoLatin1),
            let altFixed = String(data: isoData, encoding: .utf8) {
            alt = altFixed
        }

        print(alt)
        // ♫ When the spacing is tight / And the difference is slight / That's a moiré ♫
    }
} catch {
    print(error)
}

如果你只有一个表单字符串

小心\u00e2\u0080\u0094这是繁殖季节

那么你仍然可以使用JSONSerialization 来解码\uNNNN 转义序列，然后像上面那样继续。

一个简单的例子（为了简洁省略了错误检查）：

let strbad = "Be careful\\u00e2\\u0080\\u0094it's breeding season"
let decoded = try! JSONSerialization.jsonObject(with: Data("\"\(strbad)\"".utf8), options: .allowFragments) as! String
let strgood = String(data: decoded.data(using: .isoLatin1)!, encoding: .utf8)!
print(strgood)
// Be careful—it's breeding season

Answer 2

我找不到任何内置的东西，但我确实设法为你写了这个。

extension String {
    func range(nsRange: NSRange) -> Range<Index> {
        return Range(nsRange, in: self)!
    }

    func nsRange(range: Range<Index>) -> NSRange {
        return NSRange(range, in: self)
    }

    var fullRange: Range<Index> {
        return startIndex..<endIndex
    }

    var fullNSRange: NSRange {
        return nsRange(range: fullRange)
    }

    subscript(nsRange: NSRange) -> Substring {
        return self[range(nsRange: nsRange)]
    }

    func convertingUnicodeCharacters() -> String {
        var string = self
        // Characters need to be replaced in groups in case of clusters
        let groupedRegex = try! NSRegularExpression(pattern: "(\\\\u[0-9a-fA-F]{1,8})+")
        for match in groupedRegex.matches(in: string, range: string.fullNSRange).reversed() {
            let groupedHexValues = String(string[match.range])
            var characters = [Character]()
            let regex = try! NSRegularExpression(pattern: "\\\\u([0-9a-fA-F]{1,8})")
            for hexMatch in regex.matches(in: groupedHexValues, range: groupedHexValues.fullNSRange) {
                let hexString = groupedHexValues[Range(hexMatch.range(at: 1), in: string)!]
                if let hexValue = UInt32(hexString, radix: 16),
                    let scalar = UnicodeScalar(hexValue) {
                    characters.append(Character(scalar))
                }
            }
            string.replaceSubrange(Range(match.range, in: string)!, with: characters)
        }
        return string
    }
}

它基本上查找任何\u<1-8 digit hex> 值并将它们转换为标量。应该相当简单......

我的游乐场测试代码很简单：

let string = "Be careful\\u00e2\\u0080\\u0094-\\u1F496\\u65\\u301it's breeding season"
let expected = "Be careful\u{00e2}\u{0080}\u{0094}-\u{1f496}\u{65}\u{301}it's breeding season"
string.convertingUnicodeCharacters() == expected // true ?