iOS三種正則表達式

1.利用NSPredicate（謂詞）匹配 
例如匹配有效郵箱： 

1 NSString ＊email ＝ @「nijino_saki@163.com」； 
2 NSString *regex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}"; 
3 NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex]; 
4 BOOL isValid = [predicate evaluateWithObject:email];

謂詞匹配比較靈活，可是須要有謂詞的相關知識。 

2.利用rangeOfString：option：直接查找 

1 NSString *searchText = @"// Do any additional setup after loading the view, typically from a nib."; 
2 
3 NSRange range = [searchText rangeOfString:@"(?:[^,])*\\." options:NSRegularExpressionSearch]; 
4 
5 if (range.location != NSNotFound) { 
6     NSLog(@"%@", [searchText substringWithRange:range]); 
7 }

options中設定NSRegularExpressionSearch就是表示利用正則表達式匹配，會返回第一個匹配結果的位置。 

3.使用正則表達式類 

1 NSString *searchText = @"// Do any additional setup after loading the view, typically from a nib.";    
2 NSError *error = NULL;
3 NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?:[^,])*\\." options:NSRegularExpressionCaseInsensitive error:&error];
4 NSTextCheckingResult *result = [regex firstMatchInString:searchText options:0 range:NSMakeRange(0, [searchText length])];
5 if (result) {
6     NSLog(@"%@\n", [searchText substringWithRange:result.range]);
7 }

使用系統的正則表達式類（NSRegularExpression）會返回匹配的多個結果。