- (void)viewDidLoad {

    [super viewDidLoad];

    textField = [[UITextField alloc]initWithFrame:CGRectMake(, , , )];

    textField.borderStyle = UITextBorderStyleRoundedRect;

    textField.delegate = self;

    // 首先我们要设置一下键盘类型

    textField.keyboardType = UIKeyboardTypeASCIICapable;

    [self.view addSubview:textField];

}

// 直接不允许输入

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

{

    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:ALPHANUM] invertedSet];

    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

    return [string isEqualToString:filtered];

}

// 判断仅输入字母或数字：

- (BOOL) deptIdInputShouldAlphaNum: (NSString *)inputStr

{

    NSString *regex =@"[a-zA-Z0-9]*";

    NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",regex];

    if (![pred evaluateWithObject:inputStr]) {

        return YES;

    }

    return NO;

}