Question

In native C++ using Visual Studio 2008 how do I pass an interface to a class member using const? Doing the following caused this error:

error C2662: ‘IMyInterface::PublicMember1’ cannot convert ‘this’ pointer from ‘const IMyInterface’ to ‘IMyInterface &’

class IMyInterface
{
  virtual std::wstring PublicMember1() = 0;
  virtual int PublicMember2() = 0;
  virtual void Update(const IMyInterface & myObject) = 0;
}

class MyClass : public IMyInterface
{
   private:
      std::wstring privateMember1;
      int privateMember2;
   public:
      virtual std::wstring PublicMember1() { return privateMember1; }
      virtual int PublicMember2() { return privateMember2; }
      virtual void Update(const IMyInterface & myObject);
}

void MyClass::Update(const IMyInterface& myObject)
{
     privateMember1 = myObject.PublicMember1();
     privateMember2 = myObject.PublicMember2();
}

Answer 1

Declare the required methods of the interface as const

class IMyInterface
{
  virtual std::wstring PublicMember1() const = 0;
  virtual int PublicMember2() const = 0;
  virtual void Update(const IMyInterface & myObject) = 0;
}