CODEWITHSUNDEEP
qtmodel
nairware
nairware

Reputation: 3190

Qt Model/View Architecture - How to Handle More Complex Models

Is a model in Qt supposed to more or less fit the mold—and therefore ultimately be represented by—a list, table or tree? What if your model is a lot more complex and cannot be represented by a list, table or tree?

If this were the case, I would think that would make a model nothing but data; something comparable to an XML file or a spreadsheet.

Example: What if the model within the application in question were something more complex, like a car? I would assume the model of a car would include all sort of data and business rules about the car. There would be an engine, wheels, a frame, and many other different components that all work together to create the entire car. Each component would have its own unique set of behaviors: the frame would have a color, the engine would have a temperature, the stereo would have a volume setting, and so forth. And each component would have behaviors too: if the gas pedal is pressed, the wheels rotate and the engine heats up. Obviously, a QStringListModel or some other built-in, simplified model cannot appropriately address all of the complexities in a car.

Upvotes: 5

Views: 2173

Answers (2)

sashoalm
sashoalm

Reputation: 79705

A model is not data but a set of callbacks. In fact, there need not be real data staying behind the model. It is more like a server to be queried.

This is like the difference between this:

int data[5] = { 0, 2, 4, 6, 8 };
void viewer(int *data, int n) {
    for (int ii = 0; ii < n; ii++)
        printf("%d, ", data[ii]);
}
int main() {
    viewer(data, 5);
}

And this:

int model(int index) {
    return index * 2;
}
typedef int (*model_function)(int);
void viewer(model_function model, int n) {
    for (int ii = 0; ii < n; ii++)
        printf("%d, ", model(ii));
}
int main() {
    viewer(model, 5);
}

Both will give you 0, 2, 4, 6, 8, but the model doesn't actually need an array to give the same values.

Upvotes: 2

NG_
NG_

Reputation: 7181

Try to read about MV in Qt here: similar question on SO, and of course, at such resources as Model/View Programming at http://qt-project.org/. Also, there are lot of interesting videos by VoidRealms, including this theme -- VoidRealms: C++ Qt 47 - Intro to model view programming.

Try to understand it in general, and in particular case -- how it is in Qt, and all questions and yours misunderstanding will disappear.

Upvotes: 1

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