Calling virtual functions inside constructors

Question

Suppose I have two C++ classes:

class A
{
public:
  A() { fn(); }

  virtual void fn() { _n = 1; }
  int getn() { return _n; }

protected:
  int _n;
};

clas         


        

Answer 1

One solution to your problem is using factory methods to create your object.

• Define a common base class for your class hierarchy containing a virtual method afterConstruction():

class Object
{
public:
  virtual void afterConstruction() {}
  // ...
};

• Define a factory method:

template< class C >
C* factoryNew()
{
  C* pObject = new C();
  pObject->afterConstruction();

  return pObject;
}

• Use it like this:

class MyClass : public Object 
{
public:
  virtual void afterConstruction()
  {
    // do something.
  }
  // ...
};

MyClass* pMyObject = factoryNew();