Qt and C++

This chapter will, just as Qt, require the reader to have some basic knowledge of C++. Qt does not rely on advanced C++ features and I generally consider the Qt style of C++ to be very readable, so do not worry if you feel that your C++ knowledge is shaky.

Qt uses this meta information to enable a very loosely bound callback concept using signals and slots. Each signal can be connected to any number of slots or even other signals. When a signal is emitted from an object instance, the connected slots are invoked. As the signal emitting object does not need to know anything about the object owning the slot and vice versa, this mechanism is used to create very reusable components with very few inter-component dependencies.

The introspection features are also used to create dynamic language bindings, making it possible to expose a C++ object instance to QML and making C++ functions callable from Javascript. Other bindings for Qt C++ exist and besides the standard Javascript binding, the official one is the Python binding called PySide6 (opens new window).

When it comes to re-using, not only can source code be re-used but developer skills are also reusable. A team knowing Qt can reach out to far more platforms then a team just focusing on a single platform specific technology and as Qt is so flexible the team can create different system components using the same technology.

For all platform, Qt offers a set of basic types, e.g. strings with full Unicode support, lists, vectors, buffers. It also provides a common abstraction to the target platform’s main loop, and cross-platform threading and networking support. The general philosophy is that for an application developer Qt comes with all required functionality included. For domain-specific tasks such as to interface to your native libraries, Qt comes with several helper classes to make this easier.