money-rails, Money#== 仅支持零数字

Question

我在我的 Rails 应用程序中使用 money-rails gem。到目前为止，它一直运行良好，但我最近开始收到以下错误：

Money#== supports only zero numerics

我不确定是什么原因造成的，也不知道如何解决。我最近运行了bundle update，所以我猜有些东西已经更新了。我的gemfile 看起来像这样：

gem 'money-rails', '~>1'
gem 'eu_central_bank', "~>1.3.0"

我的实现如下所示：

# model
monetize :price_in_cents

# fetch / converting currencies
eu_bank = EuCentralBank.new
Money.default_bank = eu_bank
eu_bank.update_rates
converted_price = eu_bank.exchange_with(Money.new(price_to_convert * 100, from_currency), to_currency)

正如我之前提到的那样，这已经奏效了，所以我不确定是什么破坏了它。

有什么想法吗？

更新

为了测试我尝试了以下方法。

money = Money.new(100, from_currency)

然后我得到了和以前一样的错误。但如果我尝试过：

money = Money.new(0, from_currency)

它似乎工作。我觉得这有点奇怪。

更新

这是我尝试保存记录时的回溯：

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Answer 1

Money Rails 会自动将“_cents”添加到您正在获利的属性中。然后它创建一个 model.price 的实例，其中包括

<Money fractional:1500 currency:DKK>

因此，您不能执行 model.price + 10，因为这会导致您遇到错误。 因此，您可能希望将 price_to_convert 或您正在使用的任何其他价值货币化，以便您可以总结它们等。

创建一个新的迁移文件，例如 rails g 迁移 AddMoneytizeToOrders

更改迁移文件，使其如下所示（将列/属性更改为您的值）

class AddMonetizeToOrder < ActiveRecord::Migration[6.0]
  def change
    add_monetize :orders, :price_to_convert, currency: { present: false }
  end
end

在您的模型中，您必须包含

monetize :price_to_convert_cents

然后您可以使用例如（rails c）Order.last.price_to_convert + Model.last.price 等。

请注意，您不能使用 self.[:price_to_convert] 因为money rails 无法理解它并且您会收到错误

money rails ActiveModel::MissingAttributeError (can't write unknown attribute...

因此改用 self.price_to_convert

Answer 2

您在编写规范时也可能遇到此错误：

expect(order.subtotal).to eq 123.45
# ArgumentError:
#   Money#== supports only zero numerics

expect(order.subtotal).to eq Money.new(12345)
# works!

Answer 3

错误来自模型的数值验证。

Money gem 不允许将货币对象与数字进行比较，除非您的数字为零。否则，它希望您将 Money 与 Money 进行比较。

在irb你可以试试：

```红宝石

2.5.1 :006 > Money.new(1000, "USD") != Money.new(1000, "USD")
 => false 

2.5.1 :007 > Money.new(1000, "USD") != 1000
Traceback (most recent call last):
        4: from /Users/andi/.rvm/rubies/ruby-2.5.1/bin/irb:11:in `<main>'
        3: from (irb):7
        2: from (irb):7:in `!='
        1: from /Users/andi/.rvm/gems/ruby-2.5.1/gems/money-6.12.0/lib/money/money/arithmetic.rb:70:in `=='
ArgumentError (Money#== supports only zero numerics)

2.5.1 :008 > Money.new(1000, "USD") != 0
 => true 

```

我相信这个错误是有道理的，因为您无法真正将任意数字与给定货币的金额进行比较。

money-rails gem 再次带有它自己的验证器：

https://github.com/RubyMoney/money-rails#numericality-validation-options

您的回溯表明您正在使用 rails 数字验证器。