ios UITextField 输入框，几位数字后面加什么字符

@interface ViewController ()<UITextFieldDelegate>

{

    UITextField    *    _numberFielde;

}

@end

@implementation ViewController

static  NSString * NUMBER = @"0123456789";//数字

static  int  setNumber = 1; //几个数字加空格 1改成自己想要的字符

static  NSString * kongSring = @"*";//几个数字中间加的字符 x改成自己想要的字符

- (void)viewDidLoad {

    [super viewDidLoad];

    _numberFielde = [[UITextField alloc] initWithFrame:CGRectMake(10, 100,self.view.frame.size.width-20, 35)];

    _numberFielde.layer.borderColor = [UIColor grayColor].CGColor;

    _numberFielde.layer.borderWidth = 1.0f;

    _numberFielde.delegate = self;

    [_numberFielde becomeFirstResponder];

    _numberFielde.placeholder = @"请输入数字";

    [self.view addSubview:_numberFielde];

    // Do any additional setup after loading the view, typically from a nib.

}

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

    NSCharacterSet *characterSet = [[NSCharacterSet characterSetWithCharactersInString:NUMBER] invertedSet]; //定义一个字符集合 

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

    BOOL basicTest = [string isEqualToString:filtered];

    if(basicTest)

    {

      if (textField == _numberFielde)

      {

        //setNumber位加一个空格

        if ([string isEqualToString:@""]){ // 删除字符

            if ((textField.text.length - 2) % setNumber == 0) {

                textField.text = [textField.text substringToIndex:textField.text.length - 1];

            }

            return YES;

        } else {

            if (textField.text.length % setNumber == 0) {

                textField.text = [NSString stringWithFormat:@"%@%@", textField.text,kongSring];

            }

        }

        return YES;

      }

    }

    else

    {

        return NO;

    }

    return YES;

}