Question

我想编写一个可以像这样使用的函数：

let ‍‍‍ = "‍‍‍".replacingFirstOccurrence(of: "", with: "")

鉴于how odd both this string and Swift's String library are，这在Swift中是否可行？

Answer 1

根据Why are emoji characters like ?‍?‍?‍? treated so strangely in Swift strings?获得的见解，一种明智的方法可能是取代Unicode标量：

extension String {
    func replacingFirstOccurrence(of target: UnicodeScalar, with replacement: UnicodeScalar) -> String {

        let uc = self.unicodeScalars
        guard let idx = uc.index(of: target) else { return self }
        let prefix = uc[uc.startIndex..<idx]
        let suffix = uc[uc.index(after: idx) ..< uc.endIndex]
        return "\(prefix)\(replacement)\(suffix)"
    }
}

示例：

let family1 = "‍‍‍"
print(family1.characters.map { Array(String($0).unicodeScalars) })
// [["\u{0001F469}", "\u{200D}"], ["\u{0001F469}", "\u{200D}"], ["\u{0001F467}", "\u{200D}"], ["\u{0001F466}"]]

let family2 = family1.replacingFirstOccurrence(of: "", with: "")
print(family2) // ‍‍‍
print(family2.characters.map { Array(String($0).unicodeScalars) })
// [["\u{0001F469}", "\u{200D}"], ["\u{0001F469}", "\u{200D}"], ["\u{0001F466}", "\u{200D}"], ["\u{0001F466}"]]

这是一个可能的版本，它定位并替换任意字符串的Unicode标量：

extension String {
    func replacingFirstOccurrence(of target: String, with replacement: String) -> String {
        let uc = self.unicodeScalars
        let tuc = target.unicodeScalars

        // Target empty or too long:
        if tuc.count == 0 || tuc.count > uc.count {
            return self
        }

        // Current search position:
        var pos = uc.startIndex
        // Last possible position of `tuc` within `uc`:
        let end = uc.index(uc.endIndex, offsetBy: tuc.count - 1)

        // Locate first Unicode scalar
        while let from = uc[pos..<end].index(of: tuc.first!) {
            // Compare all Unicode scalars:
            let to = uc.index(from, offsetBy: tuc.count)
            if !zip(uc[from..<to], tuc).contains(where: { $0 != $1 }) {
                let prefix = uc[uc.startIndex..<from]
                let suffix = uc[to ..< uc.endIndex]
                return "\(prefix)\(replacement)\(suffix)"
            }
            // Next search position:
            uc.formIndex(after: &pos)
        }

        // Target not found.
        return self
    }
}

Answer 2

使用range(of:options:range:locale:)解决方案变得非常简洁：

extension String {
    func replaceFirstOccurrence(of searchString: String, with replacementString: String) -> String {
        guard let range = self.range(of: searchString, options: .literal) else { return self }
        return self.replacingCharacters(in: range, with: replacementString)
    }
}

首先在实例中找到searchString的范围，如果找到范围，则范围将替换为replacementString。否则，实例只返回自身。并且，由于range(of:)方法在找到匹配后立即返回，因此保证返回的范围是第一次出现。

"221".replaceFirstOccurrence(of: "2", with: "3")                // 321
"‍‍‍".replaceFirstOccurrence(of: "\u{1f469}", with: "\u{1f468}") // ‍‍‍

^{*为了澄清，最后一个测试案例将女人 - 女人 - 女孩 - 男孩转换为男女女孩。} < / p>

是否有可能编写一个Swift函数，只替换扩展字形集群的一部分，如？

2 个答案: