Rails多态关联的表单控制组

Question

In my rails app I have following models:

class Book < ApplicationRecord
   belongs_to :bookable, polymorphic: true
end

class Student < ApplicationRecord
   has_many :books, as: :bookable
end

class Library < ApplicationRecord
  has_many :books, as: :bookable
end

When creating a new book object in form.html.erb, how I could map t.integer :bookable_id and t.string :bookable_type to specific object?

Ideally I would use grouped_collection_select and pull first Student and Library and below their ids.

Thanks in advance.

Answer 1

When creating a new book object in form.html.erb, how I could map t.integer :bookable_id and t.string :bookable_type to specific object?

Well, you can use the collection_select or grouped_collection_select (according to your requirements) to display Students and Libraries to store the values for bookable_id .

For bookable_type , Rails under the hood reads the class names of the instances and captures the class name and stores it as a value for bookable_type . For example, consider the below approach

@student = Student.find(1)
@student.books.create

The above code snippet will create a record in books table with bookable_id = 1 and bookable_type = "Student"