Set shared_ptr to point existing object

Question

For the code below, I would like to know how to set std::shared_ptr to point the given objects in the two member functions. The Vector3 object whic

Answer 1

Disregarding the argument about whether using shared_ptr is a good idea or not, as explained by the accepted answer, you can use the following if you continue to use shared_ptr:

void addVtx (const Vector3& vt)
{
    vtx.push_back(std::make_shared<Vector3>(vt));
}

void setVtx (size_t v, const Vector3& vt)
{
    if ( vtx.size() > 0 && v < vtx.size() )
    {
       vtx[v] = std::make_shared<Vector3>(vt);
    }
}

Answer 2

There is not much point in using a shared_ptr for an automatically allocated object.

Technically you can do it, by giving the shared_ptr a deleter that doesn't do anything, and changing your vtx to be a vector of shared pointers to const vectors.

E.g. changing the declaration to

vector < shared_ptr <Vector3 const> > vtx;

and adding a pointer like this:

vtx.push_back( shared_ptr<Vector3 const>( &vt, [](Vector3 const*){} ) );

Disclaimer: untested code, not touched by a compiler.

However, unless you're going to also add pointers to vectors that need to be deleted, just use a vector of raw pointers. Or, just use a vector of vectors, and copy the in-data.

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It's not a good idea to use raw pointers to hold ownership. For that use smart pointers.

But conversely, it's not a good idea to use ownership smart pointers to hold pure references to static or automatic objects. For that, use raw pointers or references.

In general.