class Membership < ApplicationRecord belongs_to :user belongs_to :group before_destroy :check_last_admin protected # check if this is the last admin-membership and deny def check_last_admin raise I18n.t('model.membership.no_admin_delete') if self.group.role_admin? && self.group.memberships.size == 1 && Group.where(role_admin: true).count == 1 end end