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在 iOS 中，我们使用 NSPredicate 的字符串比较功能来进行正则表达式处理，其比较关键字为：MATCHES

下面，列举一个匹配6-15个由字母/数字组成的字符串的正则表达式，来看看 NSPredicate 的具体使用：

NSString * regex        = @"(^[A-Za-z0-9]{6,15}$)";  
NSPredicate * pred      = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];  
BOOL isMatch            = [pred evaluateWithObject:@"123456ABCde"];  

下面是一些常用的正则表达式
//邮箱

• (BOOL) validateEmail:(NSString *)email
  {
  NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}";
  NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
  return [emailTest evaluateWithObject:email];
  }

//手机号码验证

+ (BOOL) validateMobile:(NSString *)mobile  
{  
    //手机号以13， 15，18开头，八个 \d 数字字符  
    NSString *phoneRegex = @"^((13[0-9])|(15[^4,\\D])|(18[0,0-9]))\\d{8}$";  
    NSPredicate *phoneTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",phoneRegex];  
    return [phoneTest evaluateWithObject:mobile];  
}  

//车牌号验证

+ (BOOL) validateCarNo:(NSString *)carNo  
{  
    NSString *carRegex = @"^[\u4e00-\u9fa5]{1}[a-zA-Z]{1}[a-zA-Z_0-9]{4}[a-zA-Z_0-9_\u4e00-\u9fa5]$";  
    NSPredicate *carTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",carRegex];  
    NSLog(@"carTest is %@",carTest);  
    return [carTest evaluateWithObject:carNo];  
}  

//车型

+ (BOOL) validateCarType:(NSString *)CarType  
{  
    NSString *CarTypeRegex = @"^[\u4E00-\u9FFF]+$";  
    NSPredicate *carTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",CarTypeRegex];  
    return [carTest evaluateWithObject:CarType];  
}  

//用户名

+ (BOOL) validateUserName:(NSString *)name  
{  
    NSString *userNameRegex = @"^[A-Za-z0-9]{6,20}+$";  
    NSPredicate *userNamePredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",userNameRegex];  
    BOOL B = [userNamePredicate evaluateWithObject:name];  
    return B;  
}  

//密码

+ (BOOL) validatePassword:(NSString *)passWord  
{  
    NSString *passWordRegex = @"^[a-zA-Z0-9]{6,20}+$";  
    NSPredicate *passWordPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",passWordRegex];  
    return [passWordPredicate evaluateWithObject:passWord];  
}  

//昵称

+ (BOOL) validateNickname:(NSString *)nickname  
{  
    NSString *nicknameRegex = @"^[\u4e00-\u9fa5]{4,8}$";  
    NSPredicate *passWordPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",nicknameRegex];  
    return [passWordPredicate evaluateWithObject:nickname];  
}  

//身份证号

+ (BOOL) validateIdentityCard: (NSString *)identityCard  
{  
    BOOL flag;  
    if (identityCard.length <= 0) {  
        flag = NO;  
        return flag;  
    }  
    NSString *regex2 = @"^(\\d{14}|\\d{17})(\\d|[xX])$";  
    NSPredicate *identityCardPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",regex2];  
    return [identityCardPredicate evaluateWithObject:identityCard];  
}  

其实iOS中有三种方式来实现正则表达式的匹配。现在将他们都记录在这里：
1.利用NSPredicate（谓词）匹配
例如匹配有效邮箱：
NSString ＊email ＝ @“nijino_saki@163.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:0 range:NSMakeRange(0, [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。
小结：
第一种匹配需要学习NSPredicate的写法，需要查阅苹果相关技术文档；如果只关心第一个匹配的结果，第二种匹配较为简洁；如果需要匹配多个结果，同时匹配多次，第三种方式效率会更高。

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