shared_ptr pattern to own an object inside a function

Question

What's a good C++ design pattern to get an owning shared_ptr from inside a member function?

Inside my function I need to store a shared_ptr to this away and retrieve later -- in another scope. This naïve approach doesn't work:

void Foo::doSomething(shared_ptr<Bar> bar)
{
    bar->setFoo(make_shared<Foo>(this));
}

void Bar::setFoo(shared_ptr<Foo> foo)
{
    myFoo.reset(foo);
}

Now if I do

shared_ptr<Foo> foo(new Foo());
shared_ptr<Bar> bar(new Bar());
foo->doSomething(bar);

there's no way that I can later know if bar->myFoo is still valid.

The problem is that I'm creating a 2nd shared_ptr to the same Foo instance. But there's no way for me to access the shared_ptr from within the function because I only have this.

(Obviously the actual setup is more complex than this simple example)

Answer 1

You are looking for std::enable_shared_from_this and std::enable_shared_from_this::shared_from_this