如果条件在 Rails 5 ActiveRecord 条件关联中不满足，belongs_to 拒绝答案

【问题标题】：belongs_to reject if condition not meets in Rails 5 ActiveRecord Conditional Associations如果条件在 Rails 5 ActiveRecord 条件关联中不满足，belongs_to 拒绝
【发布时间】：2019-01-26 14:20:15
【问题描述】：

我有 2 个模型：

class PaymentRequest < ApplicationRecord
  has_many :invoices, ->(request) { with_currency(request.amount_currency) }
end

和

class Invoice < ApplicationRecord
  belongs_to :payment_request, optional: true
  scope :with_currency, ->(currency) { where(amount_currency: currency) }
end

PaymentRequest 可能只有相同币种的发票。并且满足条件，同时调用payment_request.invoices。

我有以下不同的货币：

payment_request = PaymentRequest.create(id: 1, amount_currency: 'USD')
invoice = Invoice.create(amount_currency: 'GBP')

但是，如何拒绝以下？

# no validation here
payment_request.invoices << invoice

# the payment_request_id is set to 1
invoice.payment_request_id #=> 1

一种解决方案是添加has_many :invoices, before_add: :check_currency 并引发异常。

有没有更好的方法来拒绝关联？

【问题讨论】：

标签： ruby-on-rails activerecord ruby-on-rails-5 belongs-to

【解决方案1】：

我实现了以下货币验证解决方案：

class PaymentRequest < ApplicationRecord
  has_many :invoices, ->(request) { with_currency(request.amount_currency) },
                      before_add: :validate_invoice

  monetize :amount_cents

  private

  def validate_invoice(invoice)
    raise ActiveRecord::RecordInvalid if invoice.amount_currency != amount_currency
  end
end

【讨论】：