//判断邮箱格式是否正确
- (BOOL)isValidateEmail:(NSString *)Email
{
    NSString *emailCheck = @"^([a-zA-Z0-9\\_\\-\\.])+@([a-zA-Z0-9_-])+((\\.[a-zA-Z0-9_-]{2,3}){1,2})$";
    NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES%@",emailCheck];
    return [emailTest evaluateWithObject:Email];
}
//判断密码格式是否正确
- (BOOL)isvalidatePassword:(NSString *)password
{
    NSString *passwordCheck = @"^(?![0-9]+$)(?![a-zA-Z]+$)[0-9A-Za-z]{8,16}$";
    NSPredicate *passwordTest = [NSPredicate predicateWithFormat:@"SELF MATCHES%@",passwordCheck];
    return [passwordTest evaluateWithObject:password];
}

用法:判断一下即可

[self isValidateEmail:emailTextField.text];
[self isvalidatePassword:passwordTextField.text];