This. A class whose name started out as an extremely abstract verb (present) having just one method (which might as well have been named :call) is a code smell,

This. A class whose name started out as an extremely abstract verb (present) having just one method (which might as well have been named :call) is a code smell, a holdover from languages that required this ceremony just to pass around and use higher-order functions. I think the furthest I would have gone is a :display_category getter in each model, and let the caller decide which collection type to end up with.