Rails 4 具有 simple_form_for、has_many 通过和嵌套属性

Question

我需要与此几乎相同的功能：

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

我一直在绕来绕去（又绕来绕去）试图让它正常运行，但让运行陷入障碍。我对 Ruby 和 Rails 还是有些陌生，在前进的过程中需要帮助。这是我目前存在的实现：

/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

所以，目前我的问题是：

表单视图中的这一行- role = ta.object.account_transfer_role.titleize
给我一个“undefined method `account_transfer_role' for nil:NilClass”错误，那么我在那里做错了什么？
为什么（或为什么会）transfer_account 模型中的 accepts_nested_attributes_for 行有效？我的印象是 accepts_nested_attributes_for 在关联的 belongs_to 端不起作用，因为它不是父级（或类似的东西）。
如果我注释掉与问题 #1 相关的代码以避免该错误，表单会呈现，但我只得到一组 account 嵌套属性的输入框。每个 transfer 在 transfers_controller 的“new”操作中构建并关联了两个 transfer_accounts 和两个 accounts（使用 transfer_account :account_transfer_role 值 'source' 和 'destination'），我不应该得到两套吗account 个嵌套属性输入框？

我的嵌套属性的 singulars/plurals 是否正确？基本上，我让他们保持一致，从他们的联想开始。例如，transfer has_many :transfer_accounts，因此 transfer_accounts 在以下所有情况下都是复数：

/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|

account也是如此，除了单数。

如果我执行第 3 步，使用提供的一组 account 属性填写表单，然后提交，我会得到一个'没有路由匹配 [POST] "/transfers/new' 错误。所以，显然我的路由有问题。我不确定 transfers 和 accounts 应该如何出现在routes.rb 文件.as
```
resources  :transfers
resources  :accounts
```
或
```
resources  :transfers do  
  resources  :accounts  
end  
```
或者还有其他方式。另外，我不知道路由文件中是否也需要 transfer_accounts。

如果您已到达此行，感谢您的耐心等待。:>) 非常感谢您提供的任何帮助。

干杯，蒂姆

Answer 1

事实证明解决方案非常简单，解决了我的问题 1、3、4 和 5 中提出的每个问题。

在表单中，我更改了这一行：

= simple_form_for :transfer do |t|

对此：

= simple_form_for @transfer do |t|

对于问题 1，account_transfer_role 不再为零。
对于问题 3，它开始为 transfer_accounts.
渲染输入框对于第4题，strong参数中的单数和复数证明是正确的，如图所示
对于问题 5，这个版本的路由被证明是正确的：

resources  :transfers
resources  :accounts

尽管我将其简化为：

resources  :transfers, :accounts

至于问题 2，我得出的最佳答案是我的理解似乎不正确，accepts_nested_attributes_for: 确实在关联的 belongs_to 方面起作用，因为它是为我工作。

我希望这对那些在 has_many, through 关联的具有嵌套属性的表单上苦苦挣扎的人有所帮助。

干杯！

Rails 4 具有 simple_form_for、has_many 通过和嵌套属性

Rails 4 with simple_form_for, has_many through and nested attributes

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