base class declaration c++ code example

Example: inheritance in c++

#include <iostream>

// Example in a game we have multiple entities so we put commom functionality and variables in base class Entity and Create Sub Classes Of the base class
class Entity {
	//This is a base class of all entities
public:
	float x =0 , y = 0;//this is the position of entity
	void Move(float xa, float ya) {
		x += xa;
		y += ya;
		//this function moves entity
	}
};
// in this example Player  inherits from public entity
class Player:public Entity// inhertiting From Entity class 
{
	// Player class is a Sub class of Entity
	//Player Class ha all the functions and var of public entity + some additional functionality and variables it is a superset of Entity

	
public : 
	const char* name = nullptr;
	void Print() {
		std::cout << name << std::endl;
	}
	//Player class has type of palyer and type of entity
	//Because it has additional method Print and var name
	//We can create entity from palyer because player has everything of entity but we can't create an Entity from player because it has additional things	
};
int main()
{
	Player D;
	D.x = 5.5f;//initializing inherited variable 
	D.y = 4.4f;//initializing inherited variable 
	D.Move(1.1f,2.2f);//Calling inherited method
	D.name = "Caleb";//initializing variable owned by player class 
	D.Print();//calling method owned by Player class
	//Now looking at the size of each class
	std::cout <<"Size of Entity was : " << sizeof(Entity) << std::endl;
	std::cout <<"Size of Player was : "<< sizeof(Player) << std::endl;
	//size of Entity output => 8
	//size of Player output => 12
	//because Entity has 2 floats = 4bytes +4 bytes =8 bytes
	//Class Player has 2floats and const char ptr which is 4 bytes for 32 bit application  = (4 +4 + 4)bytes = 12bytes 
	//Note:At the end inheretance is just a way to prevent code duplication
	std::cin.get();
}