How would I model has_many and also mark one of the 'many' as special?

rubyonrails-talk
1

I have an Image class with

belongs_to :attachable, :polymorphic => true

Titles can have Images, and so can People. In the Person class, I have the apposite relationship:

has_many :images, :as => :attachable, :dependent => :destroy accepts_nested_attributes_for :images, :reject_if => lambda { |a| a[:file].blank? && a[:file_uid].blank? && a[:file_url].blank? && a[:name].blank? }, :allow_destroy => true

This all works fine, I've got my forms working perfectly. Now I would like to mark one image as being the "portrait" for this person, and I'm stuck on how best to do this. I have done it in the past in what I recognize was a very hacky manner, just adding an image_id to the parent class and setting that in my controller. I'd rather go with the flow.

How would you add this to the models so that the relationship can be expressed in a normal nested form?

Walter

2

I'd suggest adding that a person has_one portrait, class_name: :Image. In the UI you can have them select one of their Images (or none).

-Dave

3

I would like to mark one image as being the "portrait" for this person,

I'd suggest adding that a person has_one portrait, class_name: :Image. In the UI you can have them select one of their Images (or none).

-Dave

Does that require me to add another belongs_to to the Image? If I add a has_one, won't I have to balance that on the other side?

Walter

4

I have an Image class with

belongs_to :attachable, :polymorphic => true

Titles can have Images, and so can People. In the Person class, I have the apposite relationship:

has_many :images, :as => :attachable, :dependent => :destroy accepts_nested_attributes_for :images, :reject_if => lambda { |a| a[:file].blank? && a[:file_uid].blank? && a[:file_url].blank? && a[:name].blank? }, :allow_destroy => true

This all works fine, I've got my forms working perfectly. Now I would like to mark one image as being the "portrait" for this person, and I'm stuck on how best to do this. I have done it in the past in what I recognize was a very hacky manner, just adding an image_id to the parent class and setting that in my controller. I'd rather go with the flow.

How would you add this to the models so that the relationship can be expressed in a normal nested form?

Walter

I made a little dummy app to test this out in console, and got the following to work, but (maybe it's just me) the naming seems wrong:

class Person < ActiveRecord::Base   attr_accessible :photo, :name   has_many :photos, :as => :attachment, :dependent => :destroy   belongs_to :photo end

class Photo < ActiveRecord::Base   attr_accessible :file_name, :name   belongs_to :attachment, :polymorphic => true   has_one :person end

Ignore the fact that I called it Photo rather than Image in this one...

Photo has_one person, but there are going to be instances where the attachment is to a Title (which doesn't need that relationship), and I'm not sure what happens then.

Walter

5

I would like to mark one image as being the "portrait" for this person,

I'd suggest adding that a person has_one portrait, class_name: :Image. In the UI you can have them select one of their Images (or none).

-Dave

Does that require me to add another belongs_to to the Image? If I add a has_one, won't I have to balance that on the other side?

Walter

Just tried this in my stunt app, and it would require me to add a person_id to the Photo / Image model, which since it's polymorphic, is sort of beside the point.

Walter

6

class Person < ActiveRecord::Base attr_accessible :photo, :name has_many :photos, :as => :attachment, :dependent => :destroy

I would do this. This will save a portrait_id on a person object, which is the id of a photo. This is most efficient because if you put the “belongs_to” association on the photo object, you’ll end up with many photos with nil values for person_id.

belongs_to :portrait, :class_name => “Photo” end

class Photo < ActiveRecord::Base attr_accessible :file_name, :name belongs_to :attachment, :polymorphic => true

end

7

class Person < ActiveRecord::Base   attr_accessible :photo, :name   has_many :photos, :as => :attachment, :dependent => :destroy

  # I would do this. This will save a portrait_id on a person object, which is the id of a photo. This is most efficient because if you put the "belongs_to" association on the photo object, you'll end up with many photos with nil values for person_id.   belongs_to :portrait, :class_name => "Photo" end

class Photo < ActiveRecord::Base   attr_accessible :file_name, :name   belongs_to :attachment, :polymorphic => true

Thanks for the suggestion. Would I also need to add anything to the Photo class to hold up the other side of the belongs_to? has_one :person, maybe? Or would it work without that?

Walter