Item 31. Smart Pointer Members, Part 2: Toward a ValuePtr

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Item 31. Smart Pointer Members , Part 2: Toward a ValuePtr

Difficulty: 6

Can we make life safer for ourselves and our users by devising a smart pointer class designed specifically for class membership?

1. Write a suitable ValuePtr template that is used as shown here:

    // Example 31-1 // class X {   // ... private:   ValuePtr<Y> y_; }; 

   to suit three specific circumstances:

   1. Copying and assigning ValuePtr s is not allowed.

   2. Copying and assigning ValuePtr s is allowed and has the semantics of creating a copy of the owned Y object using the Y copy constructor.

   3. Copying and assigning ValuePtr s is allowed and has the semantics of creating a copy of the owned Y object, which is performed using a virtual Y::Clone() method if present and the Y copy constructor otherwise .

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