Question

我有一个这样的模型：

class Invoice
  include Mongoid::Document
  field :local, type: String
  field :date, type: DateTime
  field :total, type: Float
end

class LogInvoice
  include Mongoid::Document
  field :date, type: Date
  field :local, type: String
  field :summary, type: Hash
end

字段摘要是这样的哈希：

summary = {invoices : 0, amount : 0.0}

对于存储的每张发票，我必须在当天创建一个LogInvoice，其中包含LogInvoice.summary [：发票]中的发票总数（发票数）以及LogInvoice中的总金额（Invoice.total的总和）。总结[：量]

如果发票存在，我必须更新当天的LogInvoice。

我无法知道某个对象是否存在，因为LogInvoice.find（）会返回异常（如果不存在），那么如何更新现有对象LogInvoice或者如果不存在则创建它？

谢谢

Answer 1

如果我理解了你的问题，你应该这样做：

my_invoice_criteria = Invoice.all # or Invoice.where date: the_date_I_want or anything else
my_invoice_criteria.each do |invoice|
 log_invoice = LogInvoice.find_or_create_by date: invoice.obtain_proper_date
 #Use this for atomic persistence
 log_invoice.inc :"summary.invoices" => 1
 log_invoice.inc :"summary.amount" => invoice.total
 #Use this for standard persistence
 log_invoice.summary[:invoices]+=1
 log_invoice.summary[:amount]+=invoice.total
 log_invoice.save
end

价： Atomic persistence文档 Standard persistence文档

使用Rails 4在Mongoid中创建或增加一个字段

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