匹配NSString中单词的开头

NSString *string = @"This is a test string.";
NSString *pattern = @"\\b[A-Za-z]";

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:nil];
NSArray *matches = [regex matchesInString:string options:0 range:NSMakeRange(0, string.length)];

for (NSTextCheckingResult *match in matches) {
    NSRange matchRange = [match range];
    NSString *matchedString = [string substringWithRange:matchRange];
    NSLog(@"Matched string: %@", matchedString);
}