Rails 5使用嵌套属性链接多态关联

Question

I got 3 models, schema like below:

class Graphic < ActiveRecord
  belongs_to :imageable, polymorphic: true, optional: true
end

class SampleA < ActiveRecord
  has_one :graphic, as: :imageable
  accepts_nested_attributes_for :graphic
end

class SampleB < ActiveRecord
  has_one :graphic, as: :imageable
  accepts_nested_attributes_for :graphic
end

UPDATE, controller is here:

class SampleAscontroller < ApplicationController
  def create
    sample_a = SampleA.new sample_a_params

    if sample_a.valid? && sample.save
      render json: sample_a and return
    end

    render json: sample_a.errors.full_messages, status: 406
  end

  private

  def sample_a_params
    params.require(:sample_a).permit(
      graphic_attributes: [:id]
    )
  end
end

First, create a Graphic instance in an action, then got graphic.id = 1 .
Then, create SampleA or SampleB , parameters like { graphic_attributes: { id: 1 } }

But it throw 404 exception out, without any SQL query like select * from graphics where id = 1 .

Do I miss anything?
And how could I link the SampleA (or SampleB) to an existing Graphic when creating.

Very apperciate.

Answer 1

When you provide 'id' in nested attributes, rails tries to find in the database a Graphic with a given id, which belongs to given sample already , and update this record.

You can connect association just like this:

graphic.imageable = sample_obj
graphic.save

or

sample_obj.graphic = graphic
sample_obj.save