DynamicCasting.md

Dynamic Casting

The type system isn't enforced in C++, we can in fact cast from any type if we really want.

Dynamic cast it is specifically used for cast along the inheritance hierarchy.

Dynamic cast is one of the other casting available in C++, provided as somewhat like a safety net for when we want a specific type of cast.

It does an extra work, to ensure that this cast is valid, this validation happens at Run time, as the other types of cast usually happens at Compile time. Because of that we have a small performance cost as one should expect.

We can Enable / Disable RTTI (Run-Time Type Information) in Visual Studio by going to our Project Properties -> C/C++ -> Language -> Enable RTTI. But then we are not allowed to use dynamic cast.

Example

class Entity
{
public:
    // we need to supply this to enforce a polimorphic class
    virtual void PrintName() {}
};

class Player : public Entity {};

class Enemy : public Entity {};

int main()
{
    Player *player = new Player();
    Entity *actuallyEnemy = new Enemy();

    Entity *actuallyPlayer = player;

    // p0 will cast
    Player* p0 = dynamic_cast<Player*>(actuallyPlayer);

    if (p0)
    {
        // do something with p0
    }

    // p1 will be a nullptr because the cast wasn't possible
    Player* p1 = dynamic_cast<Player*>(actuallyEnemy);

    if (p0)
    {
        // do something with p1
    }