If we want that when we tap on a UITextField then date picker should show, so we can use following code-

 [yourTextFieldOutlet setInputView:_datePicker];// _datePicker is the DatePicker type property

Here we want to add done button on a DatePicker and once click on it DatePicker should hide.

 UIToolbar *toolBar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
    toolBar.barStyle = UIBarStyleBlackOpaque;
    
    UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(doneTouched:)];
    
    [toolBar setItems:[NSArray arrayWithObjects:doneButton,nil]];
    _yourTextFieldOutlet.inputAccessoryView = toolBar; 
- (void)doneTouched:(UIBarButtonItem *)sender
{
    // hide the picker view
    [_yourTextFieldOutlet resignFirstResponder];
    
    // perform some action
}