Observers can be registered with instances of this class so
that they are notified when a different value is assigned to
such instances. Client code can copy the contained value or
pass it to functions via implicit conversion.
note it is not possible to call non-const method on the
returned value. This is by design, as this possibility
would necessarily bypass the notification code; client
code should modify the value via re-assignment instead.
observable and assignable proxy to concrete value
Observers can be registered with instances of this class so that they are notified when a different value is assigned to such instances. Client code can copy the contained value or pass it to functions via implicit conversion. note it is not possible to call non-const method on the returned value. This is by design, as this possibility would necessarily bypass the notification code; client code should modify the value via re-assignment instead.