What's the difference between virtual and override in C++?

16 Tem 21:56

Virtual and override play crucial roles in C++ when using *polymorphism* to control hierarchy and behavior. **virtual** "announces" to the class (and its inheritors) that a method can be overridden in the future. For example, you can **override** a `virtual void render() {}` method in the *Base* class by defining `override void render() {...}` in the *Derived* class—this ensures the correct method is called at runtime. So, when working with objects through pointers or references, C++ decides which class's method to invoke. **override** not only informs the compiler that this method is overriding a virtual method but also catches common errors like signature mismatches (e.g., trying to override `virtual void foo(int x)` with `void foo(float x)` will result in a compilation error). In the projects I’ve worked on, especially in *game engines*, I frequently see this mechanism in action: for instance, the `Entity` base class defines a `virtual void update(float dt)` method, and classes like `Player`, `Enemy`, and `Particle` override it to suit their needs. This way, you can manage all objects in a single array within an *EntityManager* and call `update()` in the *Game loop*—thanks to *polymorphism*, the correct `update` method is automatically invoked at runtime. To **prevent errors**, you can also use the `final` keyword (e.g., `virtual void foo() final`), which blocks subclasses from overriding the method. In short: **virtual** = "this method can be overridden," **override** = "I am the overridden version of this virtual method, and my signature is correct," and **polymorphism** is the underlying mechanism that makes this system work.