virtual function specifier

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Syntax

Erklrung

Hier verweisen wir auf die bergeordnete Funktion als Derived::f() und der berschriebenen Funktion als Base::f()

Original:

Here we refer to the overriding function as Derived::f() and to the overridden function as Base::f()

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• beide sind Zeiger oder Referenzen auf Klassen. Multi-Level-Zeiger oder Referenzen sind nicht erlaubt .

  Original:

  both types are pointers or references to classes. Multi-level pointers or references are not allowed.

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• die Klasse der Rckgabetyp Base::f() muss eine eindeutige und leicht zugngliche direkte oder indirekte Basisklasse der Klasse der Rckgabetyp Derived::f() sein .

  Original:

  the class of the return type of Base::f() must be a unambiguous and accessible direct or indirect base class of the class of the return type of Derived::f().

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• der Rckgabetyp Derived::f() muss gleich oder weniger cv-qualifiziert als der Rckgabetyp Base::f() sein .

  Original:

  the return type of Derived::f() must be equally or less cv-qualifiziert than the return type of Base::f().

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Beispiel

class Parent {
public:
    void functionA();
    virtual void functionB();   //Note the keyword virtual
    void functionC();
};
 
class Child : public Parent {
public:
    void functionA();
    virtual void functionB();   //Note the keyword virtual
};
 
int main()
{
    Parent* p1 = new Parent;
    Parent* p2 = new Child;
    Child* c = new Child;
 
    p1->functionA();   //Calls Parent::functionA
    p1->functionB();   //Calls Parent::functionB
    p1->functionC();   //Calls Parent::functionC
   
    p2->functionA();   //Calls Parent::functionA because p2 points to a Parent
    p2->functionB();   //Calls Child::functionB even though p2 points 
                       // to a Parent because functionB is virtual
    p2->functionC();   //Calls Parent::functionC
 
    c->functionA();   //Calls Child::functionA
    c->functionB();   //Calls Child::functionB
    c->functionC();   //Calls Parent::functionC
 
    return 0;
}

Siehe auch

• berschreibungsspezifizierer (seit C++11)
• endgltigen Spezifizierer (seit C++11)