Question

How would I do this? Right now it’s creating nil values when user is male, and then the <==> operation is failing.

@user.max_by{|user_id, user| user.height if user.female?}

Answer 1

You can chain these together, so do your selection before your aggregation

@user.select{|user| user.female?}.max_by{|user_id, user| user.height}

Also, you should be able to simplify (just a little syntax sugar):

@user.select(&:female?).max_by(&:height)