(C++) Downcast

include <iostream>

//---------------------------------------------------------------------------
struct Base
{
  Base(const int& value) : mValueBase(value) {}
  virtual void doCout() const { std::cout << "Base: " << mValueBase << std::endl; }
  const int mValueBase;
};
//---------------------------------------------------------------------------
struct Derived : public Base
{
  Derived(const int& value1, const int& value2) : Base(value1), mValueDerived(value2) {}
  virtual void doCout() const
  {
    std::cout << "Derived: " << mValueBase << " " << mValueDerived << std::endl;
  }
  const int mValueDerived;
};
//---------------------------------------------------------------------------
void funcDerived(const Derived * derived)
{
  //Does nothing
  std::cout << "funcDerived called for Derived with values "
    << derived->mValueBase << " and " << derived->mValueDerived << std::endl;
  derived;
}
//---------------------------------------------------------------------------
int main()
{
  const Base * poly = new Derived(3,4);
  //funcDerived(poly); //Does not work: Cannot convert 'const Base *' to 'const Derived *'
  funcDerived(dynamic_cast<const Derived*>(poly)); //Works after downcasting with dynamic cast
}

Code links

• ::,scope operator
• <<,stream out operator
• #include
• assert
• char
• cout
• endl
• for
• #include
• int
• iostream
• main
• return
• scope operator,::
• std
• stream out operator, <<