When designing container classes in C++, it’s important to choose the appropriate smart pointers to manage the lifetime of objects stored in the container. Two commonly used smart pointers are std::unique_ptr and std::shared_ptr, each with their unique ownership semantics. In this blog post, we’ll explore when and how to use these smart pointers in container classes.

std::unique_ptr

std::unique_ptr provides exclusive ownership of an object. This means that only one std::unique_ptr can own an object at any given time. When the owning std::unique_ptr is destroyed or reset, it automatically deletes the object it owns.

#include <memory>
#include <vector>

class Container {
private:
    std::vector<std::unique_ptr<MyClass>> elements;

public:
    void addElement(std::unique_ptr<MyClass> element) {
        elements.push_back(std::move(element));
    }

    // Other member functions...
};

In the above example, we have a container class called Container that uses std::vector to store std::unique_ptr objects pointing to instances of MyClass. The addElement function takes ownership of a std::unique_ptr object and adds it to the vector. When the container is destroyed, all the owned MyClass objects will be automatically deleted.

std::shared_ptr

std::shared_ptr provides shared ownership of an object. Multiple std::shared_ptr instances can share ownership of the same object. The object will only be deleted when the last std::shared_ptr owning it is destroyed or reset.

#include <memory>
#include <vector>

class Container {
private:
    std::vector<std::shared_ptr<MyClass>> elements;

public:
    void addElement(std::shared_ptr<MyClass> element) {
        elements.push_back(element);
    }

    // Other member functions...
};

In the above example, the Container class uses std::vector to store std::shared_ptr objects pointing to instances of MyClass. The addElement function accepts a std::shared_ptr object and adds it to the vector. Since multiple std::shared_ptr instances can own the same object, the object will be deleted only when the last std::shared_ptr goes out of scope.

Conclusion

Choosing the appropriate smart pointer for managing object ownership in container classes is crucial for memory management and avoiding potential memory leaks. Use std::unique_ptr when ownership of an object needs to be exclusive, and a single owner is responsible for its deletion. Use std::shared_ptr when multiple owners can share the same object and the object should be deleted when the last owner is destroyed.

By leveraging the power of smart pointers, we can ensure safer and more efficient memory management in our container classes.

#C++ #SmartPointers