rails_admin插件在has_many：through关系上使用嵌套表单的问题

Question

I have what seems to be a cookie cutter problem that even has an associated wiki page here: https://github.com/sferik/rails_admin/wiki/Has-many-%3Athrough-association

I'll try to be brief. I have a has_many :through relationship in an application I'm building. The models involved are the following:

Athlete, AthleteRole, SportRole.

The sport_roles table has a list of generic roles that an athlete can have such as first baseman, second baseman, etc. The athlete_roles table is the many to many join table that contains an athlete_id and a sport_id.

My models are defined below with code examples. I simply want to be able to create an Athlete and associate them with 1+ sport roles (which will ultimately create 1+ new records in the athlete_roles table). It shouldn't ask me for an athlete_id as the athlete won't have an id until save is called on the backend and validation passes. I don't need to be able to create new sport_roles here. We'll assume all roles that the new athlete being created can take on have already been predefined.

** EDIT **

To clarify, my question is, how do I get to pick one or multiple existing sport roles for an athlete using the rails_admin plugin, NOT in a stand alone form ? I do not wish to create new sport roles, but I want to be able to pick an existing one or two when creating an athlete and have that data reflected in the athlete_roles table.

Code below.

class Athlete < ActiveRecord::Base

   has_many :athlete_roles, :dependent => :delete_all, :autosave => true, :include => :sport_role
   has_many :sport_roles, :through => :athlete_roles

  attr_accessible :first_name
  attr_accessible :middle_name
  attr_accessible :last_name
  attr_accessible :suffix_name
  attr_accessible :birthdate


  # FOR RAILS_ADMIN
  # for a multiselect widget:
  attr_accessible :sport_role_ids
  accepts_nested_attributes_for :athlete_roles, :allow_destroy => true
  attr_accessible :athlete_roles_attributes
end

class AthleteRole < ActiveRecord::Base

  attr_accessible :athlete_id
  attr_accessible :sport_role_id

  # Associations
    belongs_to :athlete
    belongs_to :sport_role

    # validations
    validates :athlete_id,:presence=>true,:uniqueness=>{:scope => [:sport_role_id], :message => "is already associated with this Sport Role"}
  validates :sport_role_id,:presence=> true
end

class SportRole < ActiveRecord::Base

  has_many :athlete_roles, :dependent => :delete_all
  has_many :athletes, :through => :athlete_roles

  attr_accessible :name
  attr_accessible :short_name
  attr_accessible :description
  attr_accessible :created_at
  attr_accessible :updated_at

  attr_accessible :athlete_ids
  attr_accessible :athlete_role_ids

  validates :name, :presence => true
  validates :short_name, :presence => true
  validates :description,:length=>{:maximum => 500, :allow_nil => true}

end

Answer 1

I think the problem here resides in your model.

A model like you are describing, is a has and belongs to many relation and should look like so:

athlete:

class Athlete < ActiveRecord::Base
  has_and_belongs_to_many :sport_roles
end

sports role

class SportRole < ActiveRecord::Base
  has_and_belongs_to_many :athletes
end

The migrations should look like:

athlete

class CreateAthletes < ActiveRecord::Migration
  def change
    create_table :athletes do |t|
      t.timestamps    
    end
  end
end

sports role

class CreateSportRoles < ActiveRecord::Migration
  def change
    create_table :sport_roles do |t|
      t.timestamps    
    end
  end
end

relation between athletes and sports roles

class SportRolesAthletes < ActiveRecord::Migration
  def change
    create_table :sport_roles_athletes , :id => false do |t|
      t.integer :sport_role_id
      t.integer :athlete_id
    end
  end
end