在代码开发过程中，我们经常需要用来校验邮箱、手机号等等，这个时候就需要用到正则表达式。在iOS开发中，能用来做正则校验的有两个 NSPredicate 和 NSRegularExpression 。

NSPredicate

NSPredicate 能用来简单做正则校验，但是它的问题是存在校验不出来的情况。

//NSString+RegEx.h
#import <Foundation/Foundation.h>
@interface NSString (RegEx)
#pragma mark - NSPredicate
- (BOOL)mars_matchedByPrdicateToRegEx:(NSString *)regEx;
@end
//NSString+RegEx.m
#import "NSString+RegEx.h"
@implementation NSString (RegEx)
#pragma mark - NSPredicate
- (BOOL)mars_matchedByPrdicateToRegEx:(NSString *)regEx{
  NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regEx];
  return [predicate evaluateWithObject:self];
}

@end

NSRegularExpression （推荐）

NSRegularExpression 相对于 NSPredicate 功能就强大的多了，这也是iOS正则校验的正统路子。

//NSString+RegEx.h
#import <Foundation/Foundation.h>

@interface NSString (RegEx)

#pragma mark - NSRegularExpression

//校验是否匹配
- (BOOL)mars_matchedToRegEx:(NSString *)regEx;

//匹配到的第一个字符串
- (NSString *)mars_firstMatchToRegEx:(NSString *)regEx;

//所有匹配的字符串
- (NSArray *)mars_matchesToRegEx:(NSString *)regEx;

//替换匹配到的字符串
- (NSString *)mars_stringByReplaceMatchesToRegEx:(NSString *)regEx replaceString:(NSString *)replaceString;

@end

//NSString+RegEx.m
#import "NSString+RegEx.h"

@implementation NSString (RegEx)

#pragma mark - NSRegualrExpression

//校验是否匹配
- (BOOL)mars_matchedToRegEx:(NSString *)regEx{
  
  NSError *error;
  NSRegularExpression *regularExpression = [NSRegularExpression regularExpressionWithPattern:regEx options:NSRegularExpressionCaseInsensitive error:&error];
  
  NSUInteger number = [regularExpression numberOfMatchesInString:self options:0 range:NSMakeRange(0, self.length)];
  return number != 0;
}

//匹配到的第一个字符串
- (NSString *)mars_firstMatchToRegEx:(NSString *)regEx{
  NSError *error;
  NSRegularExpression *regularExpression = [NSRegularExpression regularExpressionWithPattern:regEx options:NSRegularExpressionCaseInsensitive error:&error];
  NSTextCheckingResult *firstMatch = [regularExpression firstMatchInString:self options:0 range:NSMakeRange(0, self.length)];
  if (firstMatch) {
    NSString *result = [self substringWithRange:firstMatch.range];
    return result;
  }
  return nil;
}

//所有匹配的字符串
- (NSArray *)mars_matchesToRegEx:(NSString *)regEx{
  NSError *error;
  NSRegularExpression *regularExpression = [NSRegularExpression regularExpressionWithPattern:regEx options:NSRegularExpressionCaseInsensitive error:&error];
  
  NSArray *matchArray = [regularExpression matchesInString:self options:0 range:NSMakeRange(0, self.length)];
  
  NSMutableArray *array = [NSMutableArray array];
  if (matchArray.count != 0) {
    for (NSTextCheckingResult *match in matchArray) {
      NSString *result = [self substringWithRange:match.range];
      [array addObject:result];
    }
  }
  
  return array;
}

//替换匹配到的字符串
- (NSString *)mars_stringByReplaceMatchesToRegEx:(NSString *)regEx replaceString:(NSString *)replaceString{
  NSError *error;
  NSRegularExpression *regularExpression = [NSRegularExpression regularExpressionWithPattern:regEx options:NSRegularExpressionCaseInsensitive error:&error];

  return [regularExpression stringByReplacingMatchesInString:self options:0 range:NSMakeRange(0, self.length) withTemplate:replaceString];
}

@end

最后我们看到，还是推荐大家使用NSRegularExpression来做正则的校验，如果大家在学习中有更好的解决方法或者心得，可以在下方的留言区讨论。

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