Ruby on Rails：从对象数组创建求和数组

发布于 2024-12-21 09:01:49 字数 1087 浏览 3 评论 0原文

我有一个如下所示的对象数组：

[#<Holding id: 5, user_id: 21, outcome_id: 7, quantity: 200, cost_basis: nil, created_at: "2011-12-15 20:52:05", updated_at: "2011-12-15 20:52:05">,
 #<Holding id: 6, user_id: 21, outcome_id: 7, quantity: 750, cost_basis: nil, created_at: "2011-12-15 21:31:30", updated_at: "2011-12-15 21:31:30">,
 #<Holding id: 7, user_id: 21, outcome_id: 9, quantity: 1231, cost_basis: nil, created_at: "2011-12-15 21:35:31", updated_at: "2011-12-15 21:35:31">]

我通过使用模型的 find_all_by_user_id (Holding.find_all_by_user_id(21)) 检索了它。然而，我需要的是一系列总和。因此，举例来说，在这种情况下我想要得到的是：

[#<Holding id: 5, user_id: 21, outcome_id: 7, quantity: 950, cost_basis: nil, created_at: "2011-12-15 20:52:05", updated_at: "2011-12-15 20:52:05">,
     #<Holding id: 7, user_id: 21, outcome_id: 9, quantity: 1231, cost_basis: nil, created_at: "2011-12-15 21:35:31", updated_at: "2011-12-15 21:35:31">]

如果我可以从我的 Outcomes 模型中提取 Outcome.description 并将其与 id 一起放入第二个数组中，那么效果会更好。我是否只需要循环并在outcome_id 匹配的地方创建总和，还是有更好的方法？

原文

I have an array of objects that looks like this:

[#<Holding id: 5, user_id: 21, outcome_id: 7, quantity: 200, cost_basis: nil, created_at: "2011-12-15 20:52:05", updated_at: "2011-12-15 20:52:05">,
 #<Holding id: 6, user_id: 21, outcome_id: 7, quantity: 750, cost_basis: nil, created_at: "2011-12-15 21:31:30", updated_at: "2011-12-15 21:31:30">,
 #<Holding id: 7, user_id: 21, outcome_id: 9, quantity: 1231, cost_basis: nil, created_at: "2011-12-15 21:35:31", updated_at: "2011-12-15 21:35:31">]

I retrieved this by using my model's find_all_by_user_id (Holding.find_all_by_user_id(21)). What I need, however, is an array of sums. So, for instance, what I'd like to get instead in this instance is:

[#<Holding id: 5, user_id: 21, outcome_id: 7, quantity: 950, cost_basis: nil, created_at: "2011-12-15 20:52:05", updated_at: "2011-12-15 20:52:05">,
     #<Holding id: 7, user_id: 21, outcome_id: 9, quantity: 1231, cost_basis: nil, created_at: "2011-12-15 21:35:31", updated_at: "2011-12-15 21:35:31">]

What would make it even better is if I could pull from my Outcomes model the Outcome.description and have it in this second array along with the id. Do I just have to loop over and create sums where outcome_id's match or is there a better way?

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何以心动 2024-12-28 09:01:49

就我个人而言，我会在 SQL 中执行此操作 - SUM(quantity) 和 GROUP BY Outcome_id。

如果你想在 Ruby 中使用它，你可以做

holdings = Holding.find_all_by_user_id(21)

sums = Hash.new(0)

holdings.each do |h|
  sums[h.outcome_id] += h.quantity
end

sums 现在是一个哈希，键是所有的outcome_ids，值是总数。

请注意，在两种解决方案（SQL 和 Ruby）中，您都将丢失其他字段（holding_id、user_id、cost_basis、timestamps）中的信息，这可能不是您想要的。

Personally, I would do this in SQL - SUM(quantity) and GROUP BY outcome_id.

If you want it in Ruby, you can do

holdings = Holding.find_all_by_user_id(21)

sums = Hash.new(0)

holdings.each do |h|
  sums[h.outcome_id] += h.quantity
end

sums is now a hash with key being all the outcome_ids and the value being the total quantity.

Please note that in both solutions (SQL and Ruby) you will lose the information in the other fields (holding_id, user_id, cost_basis, timestamps), which may not be what you want.

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