NSRegularExpression从numberOfRanges方法给出错误的结果 [英] NSRegularExpression is giving incorrect result from the numberOfRanges method

问题描述

我的代码很小

创建一个新的XCode项目并运行以下代码：

Create a new XCode project and past this code to run:

NSString *stringToCheck = @"## master...origin/master [ahead 1, behind 1]";
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"\\[(ahead) (\\d), (behind) (\\d)\\]|\\[(behind) (\\d)\\]|\\[(ahead) (\\d)\\]" options:0 error:nil];

NSArray* matches = [regex matchesInString:stringToCheck options:0 range:NSMakeRange(0, [stringToCheck length])];
NSTextCheckingResult *match = [matches firstObject];
NSUInteger numberOfRanges = [match numberOfRanges];

即时获取= 9的 numberOfRanges 这不应该是5吗？

The numberOfRanges im getting = 9. But should'nt this be 5 ?

编辑：更多信息
数据可以以3种形式出现

More information the data can come in 3 forms

1. ## master...origin/master [ahead 1, behind 1]
2. ## master...origin/master [ahead 1]
3. ## master...origin/master [behind 1]

我该如何编写代码来说明所有3种情况？不知道找到哪个匹配项，我不知道如何进行。根据下面的一个答案，似乎 [match numberOfRanges] 会返回完整的匹配计数，无论是否找到了该匹配计数。

How do i write code to account for all 3 scenarios? Without knowing which match was found, I do not know how to proceed. Based on one answer below it seems that [match numberOfRanges] will return the full match count whether or not its found.

如果数据碰巧是＃1，则 [match rangeOfIndex：0-4] 方法有效。其他索引失败。

If the data happens to be #1, then the [match rangeOfIndex:0-4] method works. Other Indexes fail.

如果数据恰好是＃2，则 [match rangeOfIndex：5-6] 方法有效。其他失败

If the data happens to be #2, then the [match rangeOfIndex:5-6] method works. Others fail

如果数据恰好是＃3，则 [match rangeOfIndex：7-8] 方法作品。其他人失败了。

If the data happens to be #3, then the [match rangeOfIndex:7-8] method works. Others fail.

那么我怎么知道哪个组被捕获了，所以我知道要搜索哪个范围？

So how do i tell which group was captured, so i know which range to search?

编辑：基于给出的答案

    if ([match rangeAtIndex:1].location != NSNotFound) { // The First capture group
        aheadCount = [stringToCheck substringWithRange:[match rangeAtIndex:2]];
        behindCount = [stringToCheck substringWithRange:[match rangeAtIndex:4]];
    } else if ([match rangeAtIndex:5].location != NSNotFound) { //The second Capture group
        aheadCount = [stringToCheck substringWithRange:[match rangeAtIndex:6]];
    } else if ([match rangeAtIndex:7].location != NSNotFound) { //The third capture group
        behindCount = [stringToCheck substringWithRange:[match rangeAtIndex:8]];
    }

推荐答案

每个组，（...），您的模式中将产生一个匹配范围，整个模式（索引为0）也会产生一个匹配范围-总共为9。使用or， | ，不会更改此值，因此编号保持一致-每个组都有唯一的编号。

Every group, (...), in your pattern will produce a matching range, as will the whole pattern (with index 0) - giving you a total of 9. The use of or, |, does not change this so numbering remains consistent - every group has a unique number.

在您的示例中，如果您查看所有范围，您都会发现对于匹配5至8， NSRange 位置的值是 NSNotFound ，因为您的字符串与包含第1组到第4组的第一个选项匹配。

In your example if you examine all the ranges you will find that for matches 5 through 8 the NSRange location value is NSNotFound as your string matches the first alternative which contains groups 1 through 4.

注意：由于每个组通过测试<$而具有唯一的数字c $ c> NSNotFound 您可以确定已匹配的替代项。

Note: As each group has a unique number by testing for NSNotFound you can determine which alternative has been matched.

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