In programming languages, polymorphism means that some code or operations or objects behave differently in different contexts.
For example, the + (plus) operator in C++:
4 + 5 <-- integer addition 3.14 + 2.0 <-- floating point addition s1 + "bar" <-- string concatenation!
In C++, that type of polymorphism is called overloading.
Typically, when the term polymorphism is used with C++, however, it refers to using virtual methods, which we'll discuss shortly.
Assume we have Employee class , Manager class , and programmer class.
and the Manager class inheritance from Employee class.
Intuition , we know the a manager is also a employee , but a employee can not be a manager .
so if we create a Employee object , this employee may be manager or programmer ,
so we can assign this object to manager or programmer ,
but in the contrast , we can not assign a manager object to employee , because not all emplyees are managers.
This is the concept of polymotphism.
class Base{protected: int m_nValue;public: Base(int nValue) : m_nValue(nValue) { } const char* GetName() { return "Base"; } int GetValue() { return m_nValue; }};class Derived: public Base{public: Derived(int nValue) : Base(nValue) { } const char* GetName() { return "Derived"; } int GetValueDoubled() { return m_nValue * 2; }};
int main(){ using namespace std; Derived cDerived(5); // These are both legal! Base &rBase = cDerived; Base *pBase = &cDerived; cout << "cDerived is a " << cDerived.GetName() << " and has value " << cDerived.GetValue() << endl; cout << "rBase is a " << rBase.GetName() << " and has value " << rBase.GetValue() << endl; cout << "pBase is a " << pBase->GetName() << " and has value " << pBase->GetValue() << endl; return 0;}
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