Class Inheritance Advanced

In C++ a class can inherit one or more classes.

Inheriting multiple classes

Let's look at the following example:

#include <string> #include <iostream> using namespace std; class A { protected: string a; public: string getA() { return a; } }; class B { protected: string b; public: string getB() { return b; } }; class C : public A, public B { private: string c; public: C(string aValue, string bBalue, string cValue) { a = aValue; b = bBalue; c = cValue; } string getC() { return c; } }; void main() { C cObject("AValue", "BValue", "CValue"); cout << cObject.getA() << endl; cout << cObject.getB() << endl; cout << cObject.getC(); }

Output:

AValue BValue CValue

Explanation:

• At line 30 class C inherits two classes - A and B.
• Because of that class C has 3 properties - a, b, c and 3 functions - getA, getB and getC.

Multilevel Inheritance

A class can inherit a class that inherits other class. A long chain can be formed.

Each child in the chain inherits functions and members from the ones before it (it's parents grandparents etc...).

Here's an example:

#include <string> #include <iostream> using namespace std; class A { protected: string a; public: string getA() { return a; } }; class B : public A { protected: string b; public: string getB() { return b; } }; class C : public B { protected: string c; public: string getC() { return c; } }; class D : public C { private: string d; public: string getD() { return d; } D(string aValue, string bValue, string cValue, string dValue) { a = aValue; b = bValue; c = cValue; d = dValue; } }; void main() { D sampleObject("AValue", "BValue", "CValue", "DValue"); cout << sampleObject.getA() << endl; cout << sampleObject.getB() << endl; cout << sampleObject.getC() << endl; cout << sampleObject.getD(); }

Output:

AValue BValue CValue DValue

Explanation:

• There is an inheritance chain: A is inherited by B. B is inherited by C. C is inherited by D.
• At line 18 class B inherits class A.
• At line 30 class C inherits class B. Class C inherits the members from B and A. So class C has members - a, b and c.
• At line 43 class D inherits class C. Class D is at the bottom of the inherit chain. So it inherits members from A, B and C. Class D has members a, b, c and d.