iOS三种正则表达式

1.利用NSPredicate（谓词）匹配 
例如匹配有效邮箱：

 NSString ＊email ＝ @“nijino_saki@.com”；
 NSString *regex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
 NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
 BOOL isValid = [predicate evaluateWithObject:email];

谓词匹配比较灵活，但是需要有谓词的相关知识。

2.利用rangeOfString：option：直接查找

 NSString *searchText = @"// Do any additional setup after loading the view, typically from a nib."; 

 NSRange range = [searchText rangeOfString:@"(?:[^,])*\\." options:NSRegularExpressionSearch]; 

 if (range.location != NSNotFound) {
     NSLog(@"%@", [searchText substringWithRange:range]);
 }

options中设定NSRegularExpressionSearch就是表示利用正则表达式匹配，会返回第一个匹配结果的位置。

3.使用正则表达式类

 NSString *searchText = @"// Do any additional setup after loading the view, typically from a nib.";
 NSError *error = NULL;
 NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?:[^,])*\\." options:NSRegularExpressionCaseInsensitive error:&error];
 NSTextCheckingResult *result = [regex firstMatchInString:searchText options: range:NSMakeRange(, [searchText length])];
 if (result) {
     NSLog(@"%@\n", [searchText substringWithRange:result.range]);
 }

使用系统的正则表达式类（NSRegularExpression）会返回匹配的多个结果。