How to Deep Copy a Polymorphic Object in C When the Derived Class is Unknown?

Polymorphic Object Copying in C

Question:

In C , how can a deep copy of an instance of a base class be created when the exact derived class is unknown?

Answer:

Utilizing Virtual Clone Method

To effectively deep copy a polymorphic object, the following approach can be used:

1. Define a virtual Clone() method in the base class Base.
2. Implement the Clone() method in each derived class to create a new instance of the corresponding derived class and copy all necessary data members.

Utilizing Covariant Return Type

However, there is a более "C " approach:

1. Define a copy constructor for each derived class.
2. Override the Clone() method in each derived class to return a new instance of the corresponding derived class using the copy constructor.

Example with Covariant Return Type:

class Base
{
public:
  virtual Base* Clone() = 0;
};

class Derivedn : public Base
{
public:
  // Call to copy constructor is implicit
  Derivedn* Clone()
  {
    return new Derivedn(*this);
  }

private:
  Derivedn(const Derivedn&) : ... {}
};

This approach is concise and conforms to the principles of polymorphism in C . It allows for seamless deep copying of objects without the need for explicit member copying in the Clone() method.

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