ios - 如何使用正则表达式查找以三个字符前缀开头的单词

Question

我的目标是计算以多个字母的指定前缀开头的单词（在字符串中）的数量。格是以“非”开头的词。所以在这个例子中......

NSString * theFullTestString = @"nonsense non-issue anonymous controlWord";

...我想获得关于“废话”和“非问题”的点击，而不是关于“匿名”或“controlWord”的点击。我的点击总数应该是 2。

所以这是我的测试代码，看起来很接近，但我尝试过的正则表达式形式都不能正常工作。此代码捕获“废话”（正确）和“匿名”（错误），但没有捕获“非问题”（错误）。它的计数是 2，但出于错误的原因。

NSUInteger countOfNons = 0;
NSString * theFullTestString = @"nonsense non-issue anonymous controlWord";
NSError *error = nil;

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"non(\\w+)" options:0 error:&error];

NSArray *matches = [regex matchesInString:theFullTestString options:0 range:NSMakeRange(0, theFullTestString.length)];

for (NSTextCheckingResult *match in matches) {
    NSRange wordRange = [match rangeAtIndex:1];
    NSString* word = [theFullTestString substringWithRange:wordRange];
    ++countOfNons;
    NSLog(@"Found word:%@  countOfNons:%d", word, countOfNons);
}

我难住了。

Answer 1

正则表达式\bnon[\w-]*应该可以解决问题

\bnon[\w-]*
^ (\b) Start of word
  ^ (non) Begins with non
     ^ ([\w-]) A alphanumeric char, or hyphen
          ^ (*) The character after 'non' zero or more times

所以，在你的情况下：

NSUInteger countOfNons = 0;
NSString * theFullTestString = @"nonsense non-issue anonymous controlWord";
NSError *error = nil;

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\\bnon[\\w-]*)" options:0 error:&error];

NSArray *matches = [regex matchesInString:theFullTestString options:0 range:NSMakeRange(0, theFullTestString.length)];

for (NSTextCheckingResult *match in matches) {
    NSRange wordRange = [match rangeAtIndex:1];
    NSString* word = [theFullTestString substringWithRange:wordRange];
    ++countOfNons;
    NSLog(@"Found word:%@  countOfNons:%d", word, countOfNons);
}

Answer 2

我认为正则表达式在这里有点矫枉过正。

NSString *words = @"nonsense non-issue anonymous controlWord";
NSArray *wordsArr = [words componentsSeparatedByString:@" "];
int count = 0;
for (NSString *word in wordsArr) {
    if ([word hasPrefix:@"non"]) {
        count++;
        NSLog(@"%dth match: %@", count, word);
    }
}

NSLog(@"Count: %d", count);

Answer 3

有更简单的方法可以做到这一点。您可以使用 NSPredicate 并使用此格式 BEGINSWITH[c] %@。

示例代码

NSPredicate *resultPredicate = [NSPredicate predicateWithFormat:@"Firstname BEGINSWITH[c] %@", text];
NSArray *results = [People filteredArrayUsingPredicate:resultPredicate];