Dealing with managed and unmanaged objects

While most CoreFoundation APIs have been annotated, some significant chunks have yet to receive attention. As of this writing, the Address Book framework seems the highest profile of the unannotated APIs, with several functions taking or returning Unmanaged-wrapped types.

An Unmanaged<T> instance wraps a CoreFoundation type T, preserving a reference to the underlying object as long as the Unmanaged instance itself is in scope. There are two ways to get a Swift-managed value out of an Unmanaged instance:

• takeRetainedValue(): returns a Swift-managed reference to the wrapped instance, decrementing the reference count while doing so—use with the return value of a Create Rule function.

• takeUnretainedValue(): returns a Swift-managed reference to the wrapped instance without decrementing the reference count—use with the return value of a Get Rule function.

 https://nshipster.com/unmanaged/