The index() function used in this case is unique to QFileSystemModel; we supply it with a directory and it returns a model index. The process of subclassing models is discussed in the section on Creating New Models. As soon as you enroll in the course, you will get access to the course content through LMS (The Learning Management System) in the form of a complete set of Videos, PPTs, PDFs, and Assignments. DotNetTricks is one of the modern platforms to learn and equip in the IT Market. The MVC and Angular course offered by DNT is exhaustive, real time and with projects which enhance the skill-set.

The standard views automatically support internal drag and drop, where items are moved around to change the order in which they are displayed. By default, drag and drop is not enabled for these views because they are configured for the simplest, most common uses. To allow items to be dragged around, certain properties of the view need to be enabled, and the items themselves must also allow dragging to occur. Qt’s drag and drop infrastructure is fully supported by the model/view framework. Items in lists, tables, and trees can be dragged within the views, and data can be imported and exported as MIME-encoded data.

Designing a model

Normally, we don’t write this as a list in JavaScript, because GOT fans know that list can get real long, but this is the easiest way to demo on the blog. MVC is popular in web applications, one of the reasons is because responsibilities are divided between the client & server. Managing the frontend and backend in smaller, separate components allows for the application to be scalable, maintainable, and easy to expand. Modern web applications are very complex, and making a change can sometimes be a big headache. These functions are where the app decides what the user will see and how. Both views have two critical functions that define what each view wants to initialize and render.

The number of strings inserted is equivalent to the number of rows specified. The commands performed on the example model have all involved accumulating a selection of items in the model. It is also possible to clear the selection, or to replace the current selection with a new one.

Using model indexes

Note that this is a non-hierarchical model, so we don’t have to worry about the parent-child relationships. If our model was hierarchical, we would also have to implement the index() and parent() functions. The table below highlights the differences between current item and selected items. In this case, we just use the geometry information provided by the view option in the item rectangle. A delegate that renders items with several elements would not use the item rectangle directly. It would position the editor in relation to the other elements in the item.

The MVC architecture pattern turns complex application development into a much more manageable process. This may be a database, file, or a simple object, such as an icon or a character in a video game. All we want is a list of the name, quantity and price of each item we need to buy this week. Below we’ll describe how we could implement some of this functionality using MVC.

Using an existing delegate

The controller accepts user input and updates the model and view accordingly. While MVC is not required in application design, many programming languages and IDEs support the MVC architecture, making it a common choice for developers. Although it seems appropriate to perform sorting and filtering operations as internal functions of views, this approach does not allow multiple views to share the results of such potentially costly operations.

Qt provides three ready-to-use view classes that present data from models in ways that are familiar to most users. QListView can display items from a model as a simple list, mvc developer or in the form of a classic icon view. QTreeView displays items from a model as a hierarchy of lists, allowing deeply nested structures to be represented in a compact way.