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@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。