Question

Creating an object and giving ownership to a container using a unique_ptr is no problem. How would one remove an element by raw pointer?

std::set<std::unique_ptr<MyClass>> mySet;

MyClass *myClass = new MyClass();
mySet.insert(std::unique_ptr<MyClass>(myClass));

// remove myClass from mySet?

Answer 1

You will need to find the iterator corresponding to the myClass element and then pass that iterator to mySet.erase(). The iterator may be found using the std::find_if algorithm with a custom Predicate functor that understands how to dereference unique_ptr and compare it to the raw pointer myClass.

You can not use the overloaded size_t set::erase ( const key_type& x ); since the raw pointer (even if wrapped in a temporary unique_ptr) will not be found in mySet.