Smart Pointer¶
Definition¶
Smart pointers are just classes that wrap the raw pointer and overload the -> and * operators; this allows them to offer the same syntax as a raw pointer.
C++11 has three types of smart pointers that are defined in the <memory> header of the Standard Library. They are:
std::unique_ptr: only itself can reference it, if you want to copy, callstd::move(ptr)std::shared_ptr: allow multiple references, keep track of the reference with reference counting, when the count == 0, the object is destroyed. Usingptr.std::reset()to destroy one reference to the ptr pointer.std::weak_ptr: std::weak_ptr models temporary ownership: when an object needs to be accessed only if it exists, and it may be deleted at any time by someone else, std::weak_ptr is used to track the object, and it is converted to std::shared_ptr to assume temporary ownership. If the original std::shared_ptr is destroyed at this time, the object's lifetime is extended until the temporary std::shared_ptr is destroyed as well.
Another use for std::weak_ptr is to break reference cycles formed by objects managed by std::shared_ptr. If such cycle is orphaned (i,e. there are no outside shared pointers into the cycle), the shared_ptr reference counts cannot reach zero and the memory is leaked. To prevent this, one of the pointers in the cycle can be made weak. cppreference.com
Last update:
January 9, 2021