Question

Part of the task I have is to create a class, which contains two lists of two other classes and create “The big 4″(constructor, copy constructor, operator=, destructor)

Here’s what I did:

using namespace std;

class A{...};
class B{...};

class C{
  list<A> a;
  list<B> b;
  public:
    C();
    ~C();
    C(const C& c);
    void operator=(const C& c);
};

C::C(){
  //How to allocate memory for a and b?
}

C::~C(){
  //How to free the memory?
}

C::C(const C& c){
  a=c.a;
  b=c.b;
}

void operator=(const C& c){
  if(&c==this) return;
  // how do I delete a and b?
  a=c.a;
  b=c.b;
}

Could you clear out the things that I don’t understand(as comments in the code). And also give advice if I haven’t done anything correctly?

Answer 1

Since you’re using values (std::list values), there is nothing to do. Your constructor will call the std::list constructors automatically, which allocate any resources needed. Your destructor will call the std::list destructor, which frees resources which it acquired.

You would need some extra work if you either hold pointers to lists (i.e. std::list<A> *a;) or lists of pointers (std::list<A*> a;') – or both (std::list<A*> *a;).