Why do you take virtual inheritance?

virtual base class, virtual Why is inheritance used? I want to know what it means.

class Foo
{
public:
    void DoSomething() { /* ... */ }
};

class Bar : public virtual Foo
{
public:
    void DoSpecific() { /* ... */ }
};

c++ virtual-inheritance

2022-09-22 22:33

2 Answers

virtual Inheritance is meaningful in multiple inheritance. virtual By inheriting, multiple instances of the inherited class are prevented from being present in the hierarchy.

class A { public: void Foo() {} };
class B : public A {};
class C : public A {};
class D : public B, public C {};

If you look at the hierarchy of the code above briefly, you will see the diamond structure as below. D inherits B and C and both B and C inherit A.

  A
 / \
B   C
 \ /
  D

In this situation, ambiguity arises.

D d;
d.Foo(); // Is this B's foo? Is it C's foo?

virtaul Inheritance is used in this situation. If you specify virtual when inheriting a class, the compiler creates only single instance.

class A { public: void Foo() {} };
class B : public virtual A {};
class C : public virtual A {};
class D : public B, public C {};

This hierarchy now has only one instance of A. Anymore d.Foo(); is unambiguous.

For more information, see here.

2022-09-22 22:33

virtual Inheritance is meaningful in multiple inheritance. virtual By inheriting, multiple instances of the inherited class are prevented from being present in the hierarchy.

class A { public: void Foo() {} };
class B : public A {};
class C : public A {};
class D : public B, public C {};

If you look at the hierarchy of the code above briefly, you will see the diamond structure as below. D inherits B and C and both B and C inherit A.

  A
 / \
B   C
 \ /
  D

In this situation, ambiguity arises.

D d;
D foo. () ; // This is b foo? C foo of?

virtaul Inheritance is used in this situation. If you specify virtual when inheriting a class, the compiler creates only single instance.

class A { public: void Foo() {} };
class B : public virtual A {};
class C : public virtual A {};
class D : public B, public C {};

This hierarchy now has only one instance of A. Anymore d.Foo(); is unambiguous.

For more information, see here.

2022-09-22 22:33

If you have any answers or tips

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