Rails数据库关联多态关联

Question

I've read a few of the help topics and the ruby documentation on PolyMorphic Associations and am still not sure if that is the way to go. After struggling with the concept and trying to figure this out, I thought of reaching out here.

What I tried so far was this, which breaks all other CRUD operations from happening in the libraries and departments models.

Normal Hours Class

class NormalHour < ApplicationRecord
  belongs_to :resource, polymorphic: true
end

Library Class

class Library < ApplicationRecord
  has_many :departments, dependent: :destroy
  has_many :normal_hours, as: :resource, dependent: :destroy

  def departments
      departments = Department.where(:library_id => self.id)
  end
end

Departments Class

class Department < ApplicationRecord
  belongs_to :library, inverse_of: :departments
  has_many :normal_hours, as: :resource, dependent: :destroy
end

The problem becomes that after adding those I can no longer add or delete anything from the libraries or departments.

Any thoughts? Tutorials? Samples? Etc?

UPDATE

+---------------+--------------+------+-----+---------+----------------+
| Field         | Type         | Null | Key | Default | Extra          |
+---------------+--------------+------+-----+---------+----------------+
| id            | int(11)      | NO   | PRI | NULL    | auto_increment |
| resource_type | varchar(255) | YES  | MUL | NULL    |                |
| resource_id   | int(11)      | YES  |     | NULL    |                |
| day_of_week   | int(11)      | YES  |     | NULL    |                |
| open          | time         | YES  |     | NULL    |                |
| close         | time         | YES  |     | NULL    |                |
| created_at    | datetime     | NO   |     | NULL    |                |
| updated_at    | datetime     | NO   |     | NULL    |                |
+---------------+--------------+------+-----+---------+----------------+

UPDATE 2

It appears that I'm having issues with the views now, but simplifying the view and modifying my Library and Department classes has fixed my original problem. Now I'm trying to figure out the best case scenario for making a dynamic form that changes the type based on selected object and loads both libraries and departments into a select field.

removed dependent: :destroy

Library Class

class Library < ApplicationRecord
  has_many :departments, dependent: :destroy
  has_many :normal_hours, as: :resource

  def departments
      departments = Department.where(:library_id => self.id)
  end
end

Departments Class

class Department < ApplicationRecord
  belongs_to :library, inverse_of: :departments
  has_many :normal_hours, as: :resource
end

UPDATE 3

Problem Update:

After Update 2 I think my true problem is figuring out the views for this stuff. I know that the department and library classes will have access to normal_hours information. The problem that I'm having is in entering the data through forms and using that same form to update that data.

  <div class="field" >
    <%= f.collection_select(:resource_id, Library.all, :id, :name)  %>
  </div>

  <div class="field">
    <%= f.collection_select(:resource_id, Department.all, :id, :reformat_name) %>
  </div>

I need a condition to turn off the fields or hide the fields based on the type of information being entered. I thought about putting a check button or question that uses JS to hide/show the correct drop down, but what kind of a logic do I need to change the specific class based on the type or is there a better way.

I was thinking that potentiall in the collection_select I could use the reference type to call the class @normal_hours.resource_type.all but I doubt that would instantiate a new class.

Answer 1

I think you've got the schema wrong for polymorphic associations. Take a look at the rails guide on polymorphic associations . Your normal_hours table should have two fields: resource_id and resource_type. Using those two keys, a NormalHour can belong to either a Library or a Department. In one case, the values in those fields would be "5" and "Library" and the other case "12" and "Department". The schema in your picture is not polymorphic - its simply that NormalHour can belong to either of those.

This could could be causing problems as well:

def departments
  departments = Department.where(:library_id => self.id)
 end

That is overriding the definition of departments with the has_many association.