如何编码“数字键盘”比如调用应用程序

// CustomNumbersView.m

- (void)button1DidClick:(id)sender
{
  [self.delegate customNumbersView:self didSelectKeyWithValue:@"1"];
}

- (void)button2DidClick:(id)sender
{
  [self.delegate customNumbersView:self didSelectKeyWithValue:@"2"];
}

// MainViewController.m

- (void)viewDidLoad
{
  [super viewDidLoad];
  CustomNumbersView *customNubmersView = [[CustomNumbersView alloc] initWithFrame:...];
  customNumbersView.delegate = self;
}

- (void)customNumbersView:(CustomNumbersView *)customNumbersView didSelectKeyWithValue:(NSString *)value
{
  self.mainTextField.text = [NSString stringWithFormat:@"%@%@", self.mainTextField.text, value];
}