Avoiding Object Slicing C++

Question

I have an issue where I'd like to copy an object, but want to avoid slicing it.

DerivedObj derivedObj;
myFunc(derivedObj);

void myFunc(MyObj &obj)
{
   MyObj *saveForLater = new MyObj(obj); // slices my object
   // ...  //
}

Is there a way to get around this? I do need to make a copy because the original object will have left scope before it is required.

@clcto Passing in a pointer versus a reference is not an issue. Pointers and references do NOT get sliced. Consider pointers and references "non-slicable". The slicing happens on the statement with the new call. — user2836797
– user2836797, Commented Jul 8, 2014 at 5:28
As far as I know, you have two main options, have a virtual method called clone() or be able to give some sort of ownership of obj to myFunc(), perhaps by using a shared_ptr<MyObj>. — Bill Lynch
– Bill Lynch, Commented Jul 8, 2014 at 5:29

Andrew Shepherd · Accepted Answer · 2014-07-08 05:29:51Z

6

If your constraints allow it, you could add a virtual Clone method.

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

 class DerivedObj : public MyObj
 {
      public:
          virtual MyObj* Clone() const 
           {
                return new DerivedObj(*this);
           }
 };




 void myFunc(MyObj &obj)
 {
      MyObj *saveForLater = obj.Clone(); 
      // ...  //
  }

answered Jul 8, 2014 at 5:29

Andrew Shepherd

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