Question

I have a superclass called DataItem and it has multiple children and the children have children too. I dynamically set the object type but in the end the type reference is DataItem. Here is the code I use to determine the class type:

private DataItem getDataItemUponType(DataSection parent,Element el) {
    String style = getItemStyle(parent,el);
    if(style!=null) {
        if(style.equals("DUZ")) {
            return new DataItemPlain();
        } else if(style.equals("TVY")) {
            return new DataItemPaired();
        } else if(style.equals("TVA")) {
            return new DataItem();
        } else if(style.equals("FRM")) {
            return new DataItemForm();
        } else if(style.equals("IMG")) {
            return new DataItemImage();
        } else if(style.equals("CLN")) {
            return new DataItemCalendar();
        } else if(style.equals("BTN")) {
            return new DataItemButton();
        } else if(style.equals("ALT")) {
            return new DataItemSubRibbon();
        }
    } else {    
        // At least return a DataItem.
        return new DataItem();
    }
    return new DataItem();
}

Then I use this to set my object:

DataItem dataItem = getDataItemUponType(parent,element);

Then I want to call from a subtype of DataItem. How do I do that?

Note: I need to use DataItem so making it abstract wouldn’t work for me.

Answer 1

You’re trying to break the idea of the abstraction: you should be fine with DataItem. It should have all the methods you would actually want to invoke. That’s the main idea:

Have an interface to describe the communication and hide the implementation.

Try to reconsider your design.