Swift 5.2正则表达式如何实现非贪婪搜索效果

在Swift 5.2中使用NSRegularExpression时，U（全局非贪婪反转）标记不受支持。此前测试中，该标记可让正则默认非贪婪，从而正确匹配两段独立的- examples:内容块；去掉U标记后，正则会贪婪匹配成一个完整大区块，无法拆分出目标内容。

需通过显式非贪婪量词（如.*?）替代U标记的效果，同时调整正则选项以支持跨多行匹配，最终获取两段独立的匹配结果。

修改后的完整代码 #

import Foundation

// 使用.*?实现非贪婪匹配，替代U标记
let pattern = #"- examples: \[\{.*?\}\}\]"#
// 启用dotMatchesLineSeparators让.匹配换行，anchorsMatchLines适配行首尾锚点
let regex = try! NSRegularExpression(pattern: pattern, options: [.anchorsMatchLines, .dotMatchesLineSeparators])
let testString = #""""
    /**
     Gets a list of custom fields.
     - GET
     - OAuth:
       - name:
     - examples: [{contentType=application/json, example={
  "s" : [ {
    "name" : "name",
  }, {
    "name" : "name",
  } ],
  "fields" : [ {
    "items" : [ "listItems", "listItems" ],
    "name" : "name",
      "message" : "message"
    },
  }, {
    "items" : [ "listItems", "listItems" ],
    "name" : "name",
  } ]
}}]
     - returns: Request<Fields>
     */

    /**
     Gets a
     - examples: [{contentType=application/json, example={
  "fields" : [ {
    "name" : "name",
  } ],
  "fields" : [ {
    "listItems" : [ "listItems", "listItems" ],
    "name" : "name",
  } ]
}}]
     - returns: Request<fields>
     */
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let matches = regex.matches(in: testString, range: stringRange)
var result: [String] = []
for match in matches {
    let nsRange = match.range(at: 0)
    guard !NSEqualRanges(nsRange, NSMakeRange(NSNotFound, 0)) else { continue }
    let string = (testString as NSString).substring(with: nsRange)
    result.append(string)
}
// 输出两段匹配结果
result.forEach { print($0 + "\n---") }

关键说明 #

1. 替换U标记：用.*?（非贪婪匹配任意字符）替代U标记的全局非贪婪效果，确保正则匹配到最近的}}]就停止，而非匹配到最后一个。
2. 正则选项调整：添加.dotMatchesLineSeparators，让.可以匹配换行符，否则无法跨多行捕获examples块内的完整内容。
3. 简化匹配逻辑：直接匹配完整的- examples: [{...}}]结构，无需多余分组，提升代码可读性。

预期输出 #

- examples: [{contentType=application/json, example={
  "s" : [ {
    "name" : "name",
  }, {
    "name" : "name",
  } ],
  "fields" : [ {
    "items" : [ "listItems", "listItems" ],
    "name" : "name",
      "message" : "message"
    },
  }, {
    "items" : [ "listItems", "listItems" ],
    "name" : "name",
  } ]
}}]
---
- examples: [{contentType=application/json, example={
  "fields" : [ {
    "name" : "name",
  } ],
  "fields" : [ {
    "listItems" : [ "listItems", "listItems" ],
    "name" : "name",
  } ]
}}]
---

内容的提问来源于stack exchange，提问作者ashokds