vicente.botet wrote:
The question is how to make X movable efficiently. The first way is to move each one of the movable objects one by one. This could be expensive if the number of members is high. In addition X can have also member that are not movable.
The second approach is to use the same technique, store a pointer to the data on a shared_pointer, and move on one operation all the members via the pointer.
Why shared_ptr? There is no sharing of ownership required. Just use std::unique_ptr.
I think that this separation is in line with the C++ principle "you don't pay for what you don't use". Any thoughts?
You're just stating the advantages and disadvantages between storing the data in the object itself and storing it in a separate object that is referenced. It's simply a tradeoff between {locality, compactness, allocation speed} and moving speed.