money-rails, Money#== 僅支持零數字

Question

我在 Rails 應用程序中使用了money-rails gem。 到目前為止，它一直運行良好，但我最近開始收到以下錯誤：

Money#== supports only zero numerics

我不確定是什么導致了這個問題或如何解決它。 我最近運行了bundle update所以我猜有些東西已經更新了。 我的gemfile看起來像這樣：

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

我的實現是這樣的：

# 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樣，這已經奏效，所以我不確定是什么破壞了它。

有任何想法嗎？

更新

為了測試，我嘗試了以下內容。

money = Money.new(100, from_currency)

然后我得到了和以前一樣的錯誤。 但如果我嘗試：

money = Money.new(0, from_currency)

它似乎工作。 我覺得這有點奇怪。

更新

這是我嘗試保存記錄時的回溯：

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Answer 1

錯誤來自對模型的數值驗證。

貨幣寶石不允許將貨幣對象與數字進行比較，除非數字為零。 否則，它希望您將 Money 與 Money 進行比較。

在 irb 你可以嘗試：

```紅寶石

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 

``

我相信這個錯誤是有道理的，因為您無法真正將任意數字與給定貨幣的金額進行比較。

money-rails gem 再次帶有自己的驗證器：

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

您的回溯顯示您正在使用 rails 數值驗證器。

Answer 2

在編寫規范時，您也可能會遇到此錯誤：

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

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

Answer 3

Money Rails 會自動將“_cents”添加到您正在獲利的屬性中。 然后它創建該 model.price 的一個實例，其中包括

 <Money fractional:1500 currency:DKK>

因此，您不能執行 model.price + 10 ，因為它會導致您得到的錯誤。 因此，您可能希望通過 price_to_convert 或您正在使用的任何其他值獲利，以便您可以將它們匯總等。

創建一個新的遷移文件，例如 rails g migration AddMoneytizeToOrders

更改遷移文件，使其讀取如下（將列/屬性更改為您的值）

 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，您必須包括

 monetize :price_to_convert_cents

然后你可以使用 eg(rails c) Order.last.price_to_convert + Model.last.price 等。

請注意，您不能使用 self.[:price_to_convert]，因為money rails 無法理解它，並且您會收到錯誤消息

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

因此使用 self.price_to_convert 代替