使用带有替换功能的正则表达式进行替换

Question

在Objective-C（适用于ios）中，我希望实现与AS3中相同的效果：

var test:String = "Abba";
var reg:RegExp = /(a)|(b)/g;

var replacement:Function = function (...args):String
{
    var $1:String = args[1];//matched 'a'
    var $2:String = args[2];//matched 'b'
    if($1)
    {
        //replace a with -
        return "-";
    }
    if ($2)
    {
        //replace b with +
        return "+";
    }
    return null;
}

var result:String = test.replace(reg, replacement);//A++-
trace(test, result);//Abba A++-

换句话说，我希望能够确定匹配的捕获组并相应地替换它，我正在寻找有关enumerateMatchesInString的示例：但找不到能解决我的问题的任何东西。

Answer 1

enumerateMatchesInString:为每个匹配调用一个带有NSTextCheckingResult的块，而rangeAtIndex:idx给出捕获子组的范围：

NSString *string = @"Abba";
NSString *pattern = @"(a)|(b)";
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
                                       options:0
                                     error:NULL];

NSMutableString *newString = [string mutableCopy];
[regex enumerateMatchesInString:string options:0 range:NSMakeRange(0, [string length])
             usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
                 NSRange r1 = [result rangeAtIndex:1];
                 if (r1.location != NSNotFound) {
                     [newString replaceCharactersInRange:r1 withString:@"-"];
                 }
                 NSRange r2 = [result rangeAtIndex:2];
                 if (r2.location != NSNotFound) {
                     [newString replaceCharactersInRange:r2 withString:@"+"];
                 }
             }];
NSLog(@"%@", newString);
// Output: A++-

如果替换字符串的长度与原始字符串的长度不同，那么它将变得稍微复杂一些，因为您必须跟踪结果字符串的长度变化：

NSMutableString *newString = [string mutableCopy];
__block int offset = 0;
[regex enumerateMatchesInString:string options:0 range:NSMakeRange(0, [string length])
             usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
                 NSRange r1 = [result rangeAtIndex:1];
                 if (r1.location != NSNotFound) {
                     r1.location += offset;
                     NSString *repl = @"---";
                     [newString replaceCharactersInRange:r1 withString:repl];
                     offset += [repl length] - r1.length;
                 }
                 NSRange r2 = [result rangeAtIndex:2];
                 if (r2.location != NSNotFound) {
                     r2.location += offset;
                     NSString *repl = @"++";
                     [newString replaceCharactersInRange:r2 withString:repl];
                     offset += [repl length] - r2.length;
                 }
             }];
NSLog(@"%@", newString);
// Output: A++++---