Mike Minaev Mike Minaev - 1 year ago 49
C++ Question

std::vector of references

I have such problem: I have class

, and if have some objects of this class,

Foo a();

I need to put this object to 2 different vectors:

std::vector<Foo> vA, vB;

and if
changes in
it should be changed in
, vectors
can be different, but they can have same objects. I know that it is possible to do with Boost, but I can't use Boost.

Answer Source

There are some possibilities:

  1. Store a vector of pointers (use if your vectors share ownership of the pointers):

    std::vector<std::shared_ptr<Foo>> vA, vB;
  2. Store a vector of wrapped references (use if the vectors do not share ownership of the pointers, and you know the object referenced are valid past the lifetime of the vectors):

    std::vector<std::reference_wrapper<Foo>> vA, vB;
  3. Store a vector of raw pointers (use if your vectors do not share ownership of the pointers, and/or the pointers stored may change depending on other factors):

    std::vector<Foo*> vA, vB;

    This is common for observation, keeping track of allocations, etc. The usual caveats for raw pointers apply: Do not use the pointers to access the objects after the end of their life time.

  4. Store a vector of std::unique_ptr that wrap the objects (use if your vectors want to handover the ownership of the pointers in which case the lifetime of the referenced objects are governed by the rules of std::unique_ptr class):

    std::vector<std::unique_ptr<Foo>> vA, vB;
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