如何在另一个字符串中查找所有出现的字符串子集并将它们替换为其他字符串？ （例如：表情替换）

Question

我正在为我的应用创建聊天功能，我们有一组自定义表情符号。

如果用户在他们的评论中键入其中一种表情的快捷方式，我们需要能够按出现顺序检测快捷方式，并将其替换为正确的表情。

例如。

let emotes = [
    "app" : "[]"
    "happy" : ":)", 
]

let userComment = "I am happy"

let expectedResult = "I am :)" // "app" was not replaced because "happy"'s "h" was found first, hence it was evaluated before "app"

考虑到同一个表情可以多次出现在一条评论中，有没有一种有效的算法来实现这一点？

我知道有range(of:) 可以找到子字符串的范围，但是考虑到我们可能有几十个表情符号，使用它似乎效率非常低。

---

更新：

请注意，表情“键”（快捷方式）可能会发生冲突，因此遍历表情字典不会是答案。我更改了示例代码以反映这一点。

Answer 1

正则表达式可用于查找任何字典键的所有匹配项，例如

(app|happy)

单词边界模式\b 可用于仅匹配完整的单词：

\b(app|happy)\b

将此方法与Replace matching regex values in string with correct value from dictionary 中的代码相结合，我们得到以下实现：

func replaceOccurrences(in string: String, fromDict dict: [String: String]) -> String {
    var result = string

    // A pattern matching any of the dictionary keys.
    let pattern = "\\b(" + dict.keys.map { NSRegularExpression.escapedPattern(for: $0)}
        .joined(separator: "|") + ")\\b"
    let regex = try! NSRegularExpression(pattern: pattern)
    let matches = regex.matches(in: string, range: NSRange(string.startIndex..., in: string))

    // Iterate in reverse to avoid messing up the ranges as the keys are replaced with the values.
    for match in matches.reversed() {
        if let range = Range(match.range, in: string) {
            // Extract key, look up replacement in dictionary, and replace in result string.
            if let replacement = dict[String(string[range])] {
                result.replaceSubrange(range, with: replacement)
            }
        }
    }

    return result
}

示例 1：

let emotes = [
    "happy" : ":)",
    "sad" : ":("
]

let userComment = "I am happy to meet you, but I am sad cos of this algorithm"
let result = replaceOccurrences(in: userComment, fromDict: emotes)
print(result) // I am :) to meet you, but I am :( cos of this algorithm

示例 2：

let emotes = [
    "app" : "[]",
    "happy" : ":)"
]

let userComment = "I am happy!"
let result = replaceOccurrences(in: userComment, fromDict: emotes)
print(result) // I am :)!