has_one：through和has_many：through在同一关联中

Question

I am trying to model a relationship between Image model and Page model with the following constraints:

1 - a page can have a maximum of one image ( 0 image is also acceptable )

2 - an image is can appear in many pages.

so the relationship could be surmised as following:

class Image < ActiveRecord :: Base
  has_many :pages, :through :imageables
end

class Page < ActiveRecord :: Base
  has_one :image, :through :imageables
end

class Imageable < ActiveRecord :: Base
  belongs_to :image
  belongs_to :page
end

Usually this associations either exist with both classes Image and Page with has_many :through or both having has_one :through Is it possible to mix between has_one :through and has_many :through in this case ? ActiveRecord does not mention this particular case

PS: I chose to use the join model way since i have other models that could have the same images as well with different constraints (has_many instead of has_one)

Thanks for your help!

Answer 1

The code above didn't work... And i found a median solution to implement the schema that i needed.

The final code looks like :

class Image < ActiveRecord :: Base
  has_many :pages, :through :imageables
end

class Page < ActiveRecord :: Base
  has_many :image, :through :imageables
  accepts_nested_attributes :images, allow_destroy => true
end

class Imageable < ActiveRecord :: Base
  belongs_to :image
  belongs_to :page
  validates_uniqueness_of :page_id
end

When i use rails_admin to edit my models, i get just the thing when it comes to add a new image and the validation in Imageable ensure the ditor do not mess around with the specifications...

It is little bit weird as a solution, but believe me, it is well adapted for the context of the app that i am developping...

I am posting it so if somebody had similar concern.