Swift中的反斜杠

Question

我想取消转义反斜杠在用户输入字符串，以使用他们的regex替换。

转义反斜杠很容易用NSRegularExpression.escapedTemplate(for: "\\n")完成。这将像预期的那样返回"\\\\n"。但是，我如何向后转换它们，例如\\n (反斜杠+ n)到\n (返回)？

Answer 1

但是，我认为不可能自动这样做，因为Swift中只有几个转义字符，您可以将它们放入数组中，循环它们，然后用未转义的版本替换所有实例。下面是我做的一个字符串扩展，它可以这样做：

extension String {
    var unescaped: String {
        let entities = ["\0", "\t", "\n", "\r", "\"", "\'", "\\"]
        var current = self
        for entity in entities {
            let descriptionCharacters = entity.debugDescription.characters.dropFirst().dropLast()
            let description = String(descriptionCharacters)
            current = current.replacingOccurrences(of: description, with: entity)
        }
        return current
    }
}

要使用它，只需访问该属性。例如,

print("Hello,\\nWorld!".unescaped) 

将打印

Hello,
World!

Answer 2

我改进了@kabiroberai的代码，使其更加实用，并删除了剩下的单个反斜杠。

extension String {
    var unescaped: String {
        let entities = ["\0": "\\0",
                        "\t": "\\t",
                        "\n": "\\n",
                        "\r": "\\r",
                        "\"": "\\\"",
                        "\'": "\\'",
                        ]

        return entities
            .reduce(self) { (string, entity) in
                string.replacingOccurrences(of: entity.value, with: entity.key)
            }
            .replacingOccurrences(of: "\\\\(?!\\\\)", with: "", options: .regularExpression)
            .replacingOccurrences(of: "\\\\", with: "\\")
    }
}

更新

在某些情况下，我发现我以前的代码不能正确地转义。

所以我更新了我的制作代码。下面是我使用的最新版本。我不确定我真的需要做这个复杂的过程，但现在看来效果更好了。

var unescaped: String {
    let entities = ["\0": "0",
                    "\t": "t",
                    "\n": "n",
                    "\r": "r",
                    "\"": "\"",
                    "\'": "'",
                    ]

    return entities
        .mapValues { try! NSRegularExpression(pattern: "(?<!\\\\)(?:\\\\\\\\)*(\\\\" + $0 + ")") }
        .reduce(self) { (string, entity) in
            entity.value.matches(in: string, range: string.nsRange)
                .map { $0.range(at: 1) }
                .reversed()
                .reduce(string) { ($0 as NSString).replacingCharacters(in: $1, with: entity.key) }
        }
}

Answer 3

这是我的逃避和未逃脱的字符串。

let given =     "{\n\t\"test\": \"this  \\ \",\n\r\t\"\'testing\': 1\r\n}\\ \0 \\"
let expected = #"{\n\t\"test\": \"this  \\ \",\n\r\t\"\'testing\': 1\r\n}\\ \0 \\"#
let expectedAscii = #"{\n\t\"test\": \"this \u{0001F603} \\ \",\n\r\t\"\'testing\': 1\r\n}\\ \0 \\"#

extension String {
    private static let escapedChars = [
        (#"\0"#, "\0"),
        (#"\t"#, "\t"),
        (#"\n"#, "\n"),
        (#"\r"#, "\r"),
        (#"\""#, "\""),
        (#"\'"#, "\'"),
        (#"\\"#, "\\")
    ]
    var escaped: String {
        self.unicodeScalars.map { $0.escaped(asASCII: false) }.joined()
    }
    var asciiEscaped: String {
        self.unicodeScalars.map { $0.escaped(asASCII: true) }.joined()
    }
    var unescaped: String {
        var result: String = self
        String.escapedChars.forEach {
            result = result.replacingOccurrences(of: $0.0, with: $0.1)
        }
        return result
    }
}

print(expected == given.escaped)
print(expectedAscii == given.asciiEscaped)
print(given.escaped.unescaped == given)
print(expected.unescaped == given)
print(expected.unescaped.escaped == expected)