You’ve gone one step too far. You don’t need to have two different tables to manage the two kinds of relationships. One of Rails’ primary objectives is to satisfy the Single Responsibility Principle. The Apartment already knows what Building it is in, and that fact is not likely to change. So instead of having a separate object to manage the relationship between the building and the maintenance person, simply ask the apartment which building it is in, if you need to know that.
Apartment
belongs_to :building
has_many :leases
has_many :tenants, through: :leases
has_many :assignments
has_many :maintenance_people, through: :assignments
Assignment
belongs_to :apartment
belongs_to :maintenance_person
Building
has_many :apartments
has_many :maintenance_people, through: :apartments
has_many :leases, through: :apartments
has_many :tenants, through: :leases
Lease
belongs_to :tenant
belongs_to :apartment
MaintenancePerson
has_many :assignments
has_many :apartments, through: :assignments
has_many :buildings, through: :apartments
Tenant
has_many :leases
has_many :apartments, through: :leases
So now you can get the building from the apartment with @apartment.building or the assignment with @assignment.apartment.building. No need for a different table to manage duplicate data. You’ve stored the data in the most specific manner possible, and you don’t have to update two tables if you want to change a maintenance person’s assignment to a different apartment.
Walter
