【2017年整理】Unit 13-Polymorphism Virtual Functions.pptVIP

* * * * * * * * * * * * * * * * * * * * Calls up the chain You can still call the overridden function: void Derived::func() { cout In Derived::func!; Base::func(); // call to base class } This is a common way to add new functionality No need to copy the old stuff! Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. * Overloading and virtuals Overloading adds multiple signatures class Base { public: virtual void func(); virtual void func(int); }; If you override an overloaded function, you must override all of the variants! Cant override just one If you dont override all, some will be hidden Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. * overloading overriding #//virtual functions restrict overloading #include iostream #include string using namespace std; class Base{ public: virtual int f() const{ coutBase::int f()\n; return 1; } virtual void f(string) const {coutBase::void f(string)\n; } virtual void g() const{} }; class Derived1:public Base{ public: void g() const{} }; class Derived2:public Base{ public: int f() const{ coutDerived2::int f()\n; return 2; } }; class Derived3:public Base{ public: void f() const{ coutDerived3::void f()\n;} }; class Derived4:public Base{ public: int f(int) const{ coutDerived4::int f(int)\n; return 4; } }; Just change return type Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. * #//virtual functions restrict overloading #include iostream #include string using namespace std; class Base{ public: virtual int f() const{ coutBase::int f()\n; return 1; } virtual void f(string) const {coutBase::void f(string)\n; } virtual void g() const{} }; class Derived1:public Base{ public: void g() const{} }; class Derived2:public Base{ public: int f() const{ coutDerived2::int f()\n; return 2; } }; class Derived3:pu