Multiple has_one relations to the same model

Question

I have a User and a Shop model (Rails 5.2) that should have multiple locations like ship_location, bill_location... How can I use the same Location multiple times for this?

The User and Shop model could look something like this

class User has_one :ship_location has_one :bill_location end class Shop has_one :ship_location has_one :bill_location has_one :contact_location end

But I can't figure out how the Location model should look like. It should be as abstract as possible, so that I don't have to define a new relationship and/or models when the Location is used for another model.

I guess I have to use some sort of polymorphism:

class Location # location has owner_id and owner_type belongs_to :owner, polymorphic: true end

But this doesn't work, because user.ship_location is ambiguous (it would look for owner_type == "User" and owner_id == 1 but because there is also a bill_location with the same owner_type and owner_id, it doesn't work).

Do I need to create separate models for this, that share the same table?

Felix · Accepted Answer · 2019-04-19 19:45:55Z

1 => Take a column (let's say location_type Or any column which can make difference between shipping location,billing location, and contact location) in Location model

class User has_one :ship_location, -> { where("location_type = ?", 'ship') }, :class_name => "Location", :dependent => :destroy has_one :bill_location, -> { where("location_type = ?", 'bill') }, :class_name => "Location", :dependent => :destroy end class Shop has_one :ship_location, -> { where("location_type = ?", 'ship') }, :class_name => "Location", :dependent => :destroy has_one :bill_location, -> { where("location_type = ?", 'bill') }, :class_name => "Location", :dependent => :destroy has_one :contact_location, -> { where("location_type = ?", 'contact') }, :class_name => "Location", :dependent => :destroy end class Location belongs_to :user belongs_to :shop # (has column 'location_type') end

2 => While creating Location provide it's respective value (i.e ship, bill, contact) example -> Let's say create location for shop for loation_type = bill

Location.create(location_type: 'ship', foo: 'bar' ...)

I think in the given code example, the third class should be Location not Shop. Will propose an edit.

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