Rails 4具有simple_form_for，has_many和嵌套属性

Question

I'm in need of functionality virtually identical to this:

https://robots.thoughtbot.com/accepts-nested-attributes-for-with-has-many-through

and I've been going around and around (and around) trying to get it to function properly, but keep running into obstacles. I'm still somewhat new to Ruby and Rails and am in need of assistance in moving forward. Here is my implementation as it currently exists:

/models/transfer.rb

class Transfer < ActiveRecord::Base

  validates :name, presence:   true,
                   uniqueness: { case_sensitive: false }

  has_many  :transfer_accounts, inverse_of: :transfer
  has_many  :accounts,          through:    :transfer_accounts

  accepts_nested_attributes_for :transfer_accounts

end


/models/transfer_account.rb

class TransferAccount < ActiveRecord::Base

  validates :account_transfer_role, presence: true

  belongs_to :account,  inverse_of: :transfer_accounts
  belongs_to :transfer, inverse_of: :transfer_accounts

  validates :account,  presence: true
  validates :transfer, presence: true

  accepts_nested_attributes_for :account

end


/models/account.rb

class Account < ActiveRecord::Base

  validates :name,           presence:   true,
                             uniqueness: { case_sensitive: false }
  validates :user_name,      presence:   true
  validates :password,       presence:   true
  validates :account_number, presence:   true,
                             uniqueness: { case_sensitive: false }
  validates :routing_number, presence:   true

  has_many :transfer_accounts, inverse_of: :account
  has_many :transfers,         through:    :transfer_accounts

  belongs_to :bank, inverse_of: :accounts

end


/models/bank.rb

class Bank < ActiveRecord::Base

  validates :name,        presence:   true,
                          uniqueness: { case_sensitive: false }
  validates :connect_uri, presence:   true

  has_many :accounts

end


/controllers/transfers_controller.rb

class TransfersController < ApplicationController

  def new
    @transfer = Transfer.new
    @transfer.transfer_accounts.build(account_transfer_role: 'source').build_account
    @transfer.transfer_accounts.build(account_transfer_role: 'destination').build_account
    @valid_banks = Bank.all.collect {|c| [c.name, c.id]}  # available banks seeded in database
  end

  def index
    @transfers = Transfer.all
  end

  def show
    @transfer = resource
  end

  def create
    @transfer = Transfer.new(transfer_params)
    if @transfer.save
      redirect_to transfers_path, notice: "Transfer Created"
    else
      redirect_to transfers_path, alert:  "Transfer Not Created"
    end
  end

  def edit
    resource
  end

  def update
    if resource.update_attributes(transfer_params)
      redirect_to transfers_path(resource),     notice: "Transfer Updated"
    else
      redirect_to edit_transfer_path(resource), alert:  "Transfer Not Updated"
    end
  end

  def destroy
    resource.destroy
  end


  private

  def resource
    @transfer ||= transfer.find(params[:id])
  end

  def transfer_params
    params.require(:transfer).
      permit(:name, :description,
             transfer_accounts_attributes:
               [:account_transfer_role,
                account_attributes:
                  [:name, :description, :user_name, :password,
                   :routing_number, :account_number
                  ]
               ])
  end

end


/controllers/banks_controller.rb

class BanksController < ApplicationController

  def index
    @bank = Bank.new
    @banks = Bank.by_last_updated_at
  end

  def show
    @bank = resource
  end

  def create
    @bank = Bank.new(bank_params)
    if @bank.save
      redirect_to banks_path, notice: "Bank Created"
    else
      redirect_to banks_path, alert: "Bank Not Created"
    end
  end

  def edit
    resource
  end

  def update
    if resource.update_attributes(bank_params)
      redirect_to banks_path(resource), notice: "Bank Updated"
    else
      redirect_to edit_bank_path(resource), alert: "Bank Not Updated"
    end
  end

  def destroy
    resource.destroy
  end


  private

  def resource
    @bank ||= Bank.find(params[:id])
  end

  def bank_params
    params.require(:bank).
      permit(:name, :description, :connection_uri)
  end

end


/views/transfers/_form.html.haml

= simple_form_for :transfer do |t|
  .form-inputs

    = t.input :name, label: "Transfer Name"
    = t.input :description, required: false, label: "Transfer Description"

    = t.simple_fields_for :transfer_accounts do |ta|

      - role = ta.object.account_transfer_role.titleize

      = ta.input :account_transfer_role, as: :hidden

      = ta.simple_fields_for :account do |a|

        = a.input :bank_id, collection:    @valid_banks,
                            include_blank: 'Select bank...',
                            id:            'bank',
                            class:         'bank_selector',
                            label:         '#{role} Bank',
                            error:         '#{role} bank selection is required.'

        = a.input :name, label: "#{role} Account Name"
        = a.input :description, required: false, label: "#{role} Account Description"
        = a.input :user_name, label: "#{role} Account User Name"
        = a.input :password, label: "#{role} Account Password"
        = a.input :account_number, label: "#{role} Account Number"
        = a.input :routing_number, label: "#{role} Account Routing Number"

  = t.submit


/db/migrate/20151102001000_create_transfers.rb

class CreateTransfers < ActiveRecord::Migration
  def change
    create_table :transfers do |t|

      t.string :name, null: false, default: ''
      t.text   :description

      t.timestamps

    end
  end
end


/db/migrate/20151102002000_create_transfer_accounts.rb

class CreateTransferAccounts < ActiveRecord::Migration
  def change
    create_table :transfer_accounts do |t|

      t.string :account_transfer_role, null: false, default: ''

      t.references :transfer, index: true
      t.references :account,  index: true

      t.timestamps null: false

    end
  end
end


/db/migrate/20151102003000_create_accounts.rb

class CreateAccounts < ActiveRecord::Migration
  def change
    create_table :accounts do |t|

      t.string  :name,           null: false, default: ''
      t.string  :description
      t.string  :user_name,      null: false, default: ''
      t.string  :password,       null: false, default: ''
      t.string  :account_number, null: false, default: ''
      t.string  :routing_number, null: false, default: ''

      t.references :bank, index: true

      t.timestamps

    end
  end
end


/db/migrate/20151102004000_create_banks.rb

class CreateBanks < ActiveRecord::Migration
  def change
    create_table :banks do |t|

      t.string :name,           null: false, default: ''
      t.string :description
      t.string :connection_uri, null: false, default: ''

      t.timestamps

    end
  end
end


/db/migrate/20151102005000_add_foreign_keys_to_transfer_accounts.rb

class AddForeignKeysToTransferAccounts < ActiveRecord::Migration
  def change

    add_foreign_key :transfer_accounts, :accounts
    add_foreign_key :transfer_accounts, :transfers

  end
end


/db/migrate/20151102006000_add_foreign_keys_to_accounts.rb

class AddForeignKeysToAccounts < ActiveRecord::Migration
  def change

    add_foreign_key :accounts, :banks

  end
end


/db/seeds.rb

Bank.create(name:           'Acme Savings and Loan',
            description:    'The number one bank in the northeast',
            connection_uri: 'https://www.acmesavings.com')
Bank.create(name:           'First Bank of Anytown',
            description:    'The first and only bank in Anytown',
            connection_uri: 'https://www.firstbankanytown.com')
Bank.create(name:           'Generibank',
            description:    'The most generic bank in the country',
            connection_uri: 'https://www.generibank.com')


/config/routes.rb

Rails.application.routes.draw do

  resources  :transfers
  resources  :accounts
  resources  :banks
  root to:   'dashboard#index'

end

So, currently my questions are:

1. This line in the form view - role = ta.object.account_transfer_role.titleize
   is giving me an " undefined method `account_transfer_role' for nil:NilClass " error, so what am I doing wrong there?

2. Why does (or why would) the accepts_nested_attributes_for line in the transfer_account model work? I was under the impression that accepts_nested_attributes_for doesn't work on the belongs_to side of an association, due to the fact that it is not the parent (or something to that effect).

3. If I comment out code related to question #1 to avoid that error, the form renders, but I'm only getting one set of input boxes for the account nested attributes. With each transfer having two transfer_accounts and two accounts built and associated with it in the " new " action of the transfers_controller (with transfer_account :account_transfer_role values of ' source ' and ' destination '), shouldn't I be getting two sets of the account nested attributes input boxes?

4. Are the singulars/plurals correct for my nested attributes? Basically, I've kept them consistent, starting from their associations. For example, transfer has_many :transfer_accounts , so transfer_accounts is plural in all of the following:

    /models/transfer.rb accepts_nested_attributes_for :transfer_accounts /controllers/transfers_controller.rb @transfer.transfer_accounts.build(account_transfer_role: 'source').build_account @transfer.transfer_accounts.build(account_transfer_role: 'destination').build_account . . . def transfer_params params.require(:transfer). permit(:name, :description, transfer_accounts_attributes: [:account_transfer_role, account_attributes: [:name, :description, :user_name, :password, :routing_number, :account_number ] ]) end /views/transfers/_form.html.haml = m.simple_fields_for :transfer_accounts do |ma| 

   The same holds true for account , except as singular.

5. If I do step 3, fill out the form with the single set of account attributes provided, then submit, I get a ' No route matches [POST] "/transfers/new ' error. So, obviously something is wrong with my routing. I wasn't sure how transfers and accounts should appear in the routes.rb file. As

    resources :transfers resources :accounts 

   or as

    resources :transfers do resources :accounts end 

   or as still some other way. Also, I didn't know if transfer_accounts was needed in the routes file as well.

If you've gotten to this line, thank you for your patience.:>) And any help you can provide would be greatly appreciated.

Cheers, Tim

Answer 1

The solution turned out to be incredibly simple, resolving each of the issues raised in my questions 1, 3, 4 and 5.

In the form, I changed this line:

= simple_form_for :transfer do |t|

to this:

= simple_form_for @transfer do |t|

For question 1, account_transfer_role was no longer nil.
For question 3, it began rendering the input boxes for both transfer_accounts .
For question 4, the singulars and plurals in the strong parameters proved to be correct as shown.
For question 5, this version of the routes proved to be correct:

resources  :transfers
resources  :accounts

although I simplified it to:

resources  :transfers, :accounts

As for question 2, the best answer I come up with is that my understanding appears to have been incorrect and that accepts_nested_attributes_for: does indeed work on the belongs_to side of an association because it is working for me.

I hope this helpful to anyone struggling with forms that have nested attributes for a has_many, through association.

Cheers!