Display objects with differing column count form a TreeModel in a TableView

Hi,

i have a design problem concerning the model/view architecture in qt 5 and i could really need some help.

Let's say i want to build an application that is capable of managing media (a media library) that can be lend. I have at least two (or more) different types of Media e.g. Book, Movie-DVD, Music-CD etc...
Therefore if have the following Classes:

- Medium (Base class with some basic member variables that all media shares)

- Book
- DVD
- CD

- User (A Person that can rent the media and give it back)


I want to be able to display all Media in a plain TableView with only the data that all media has in common, e.g. Author and Title. (for example to show which media was rent by a user)
I want to be able to display a single special Type of media, e.g. DVD in a plain TableView with all it's properties derived from the media class and the additional properies from the DVD class.

Now my problem is: How do i design the model to only use a single data source but serve the data this way to a TableView.

I already got the tip to use a TreeModel for storing the data in a tree and a QSortFilterProxyModel to filter the special types for the corresponding TableViews. But how do i tie everyting together? Is this approach the right one or is there a solution that suits the problem better?

Thanks in advance for your help.

greez trixn

Since you are only ever going to display tables, why on earth would you want to incur the complexity of a tree?

You only need a simple table model that sees all media objects and one that only sees the media objects for a certain type.
In the latter case you might want to consider having one model per data type instead of doing all the type related switching inside a single class.

Cheers,
_

First of all thanks for your input.

Yeah i asked that question on stackoverflow and the tip with the tree model was one of the answers. I realized this is not exactly what i need. I'm trying to do it like this now:

- Implement an QAbstractTableModel which is holding a list of Medium-Object pointers.
- use QSortFilterProxyModel derived model to filter relevant derived objects from Medium based on an enum type i introduced.

The intention of having only one model which actually holds the data is to be able to select entries in a TableView that only shows e.g. DVDs and delete them so they are also deleted in the Medium-Model. I don't want to have several lists that i have to keep synchronized.

Is that the approach to go for ?

Thanks for your answers.

This is a valid approach and would almost certainly provide for your needs.

However, I would choose a different approach if I were to implement that.

First, I would store the media objects in separate lists, one for each C++ type:
- no casting is required when accessing media type specific
- no filtering needed to just see one type
- still easy to list all media by just going through all lists in any order I want

These lists would be in an object that any add/remove/change operation would go through:
- the object can emit signals when data is added/removed/changed
- it can implement overall saving/loading if that is required
- it makes data handling testable without any model API

Each model would have access to this object
- the overall model's rowCount would just be the sum of all list counts
- the detail model(s) would work on a single list
- if any model affects change, it would go through the list holder object
- the signals of the list holder object would allow each model instance to notify its view(s) of change

Cheers,
_

Thanks anda_skoa. Really helpful and to the point.

Greetz trixn