使用NSRegularExpression命名捕获组

Question

NSRegularExpression是否支持命名捕获组？它看起来不像the documentation，但我想在探索替代解决方案之前检查一下。

Answer 1

iOS不支持命名分组，我所能做的就是使用Enum：

枚举：

typedef enum
{
    kDayGroup = 1,
    kMonthGroup,
    kYearGroup
} RegexDateGroupsSequence;

示例代码：

NSString *string = @"07-12-2014";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\\d{2})\\-(\\d{2})\\-(\\d{4}|\\d{2})"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];

NSArray *matches = [regex matchesInString:string
                                  options:0
                                    range:NSMakeRange(0, [string length])];
for (NSTextCheckingResult *match in matches) {
    NSString *day = [string substringWithRange:[match rangeAtIndex:kDayGroup]];
    NSString *month = [string substringWithRange:[match rangeAtIndex:kMonthGroup]];
    NSString *year = [string substringWithRange:[match rangeAtIndex:kYearGroup]];


    NSLog(@"Day: %@, Month: %@, Year: %@", day, month, year);
}

Answer 2

iOS 11使用-[NSTextCheckingResult rangeWithName:] API引入了命名捕获支持。

要获取带有相关值的命名捕获字典，您可以使用此扩展（用Swift编写，但可以从Objective C调用）：

@objc extension NSString {
    public func dictionaryByMatching(regex regexString: String) -> [String: String]? {
        let string = self as String
        guard let nameRegex = try? NSRegularExpression(pattern: "\\(\\?\\<(\\w+)\\>", options: []) else {return nil}
        let nameMatches = nameRegex.matches(in: regexString, options: [], range: NSMakeRange(0, regexString.count))
        let names = nameMatches.map { (textCheckingResult) -> String in
            return (regexString as NSString).substring(with: textCheckingResult.range(at: 1))
        }
        guard let regex = try? NSRegularExpression(pattern: regexString, options: []) else {return nil}
        let result = regex.firstMatch(in: string, options: [], range: NSMakeRange(0, string.count))
        var dict = [String: String]()
        for name in names {
            if let range = result?.range(withName: name),
                range.location != NSNotFound
            {
                dict[name] = self.substring(with: range)
            }
        }
        return dict.count > 0 ? dict : nil
    }
}

来自Objective-C的电话：

(lldb) po [@"San Francisco, CA" dictionaryByMatchingRegex:@"^(?<city>.+), (?<state>[A-Z]{2})$"];
{
    city = "San Francisco";
    state = CA;
}

代码说明：该函数首先需要找出命名捕获的列表。不幸的是，Apple没有为此发布API（rdar://36612942）。

Answer 3

由于支持iOS 11命名的捕获组。请在此处查看我的回答https://stackoverflow.com/a/47794474/1696733

Answer 4

从iOS 11开始，我可以使用NSTextCheckingResult的扩展名来获取命名组的值：

extension NSTextCheckingResult {
    func match(withName name: String, in string: String) -> String? {
        let matchRange = range(withName: name)
        guard matchRange.length > 0 else {
            return nil
        }
        let start = string.index(string.startIndex, offsetBy: matchRange.location)
        return String(string[start..<string.index(start, offsetBy: matchRange.length)])
    }
}

用法：

let re = try! NSRegularExpression(pattern: "(?:(?<hours>\\d+):)(?:(?<minutes>\\d+):)?(?<seconds>\\d+)", options: [])
var str = "40 16:00:00.200000"

let result = re.firstMatch(in: str, options: [], range: NSRange(location: 0, length: str.count))
result?.match(withName: "hours", in: str)  // 16