如何使用“地图”？ ActiveRecord 类方法中的方法？

发布于 2024-09-14 04:21:06 字数 578 浏览 6 评论 0原文

不确定我的 Ruby 语法。

我想定义一个可以像这样调用的方法：client.invoices.average_turnaround。因此，我的 average_turnaround 方法需要使用 ActiveRecord 对象的集合。

到目前为止，这是我的代码：

class Invoice < ActiveRecord::Base
  ...
  def self.average_turnaround
    return self.map(&:turnaround).inject(:+) / self.count
  end
end

因此，我试图找到每张发票的周转时间总和，然后将其除以发票总数。

Ruby 抱怨没有为 Class 定义 map 方法。我期望 self 是一个 Array。

如何编写一个适用于 Invoices 集合并使用 map 函数的方法？我哪里出错了？

原文

Not sure on my Ruby syntax here.

I want to define a method that I can call like this: client.invoices.average_turnaround. So my average_turnaround method needs to work with a collection of ActiveRecord objects.

Here's my code thus far:

class Invoice < ActiveRecord::Base
  ...
  def self.average_turnaround
    return self.map(&:turnaround).inject(:+) / self.count
  end
end

So I'm trying to find the sum of the turnaround times for each invoice, then divide it by the total number of invoices.

Ruby is complaining that there is no map method defined for Class. I was expecting self to be an Array.

How do I write a method that works on a collection of Invoices and uses the map function? Where am I going wrong?

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荒路情人 2024-09-21 04:21:06

如果您想在类方法中使用映射而不是通过关联扩展。例如，如果直接调用 Invoice.average_turnaround 或 Invoice.where(x: y).average_turnaround 很有用。将 all. 放在 map 前面。

class Invoice < ActiveRecord::Base
  ...
  def self.average_turnaround
    all.map(&:turnaround).inject(:+) / all.count
  end
end

使用任何集合使用average_turnaround。

If you want to use map within the class method as opposed to through an association extension. For example if it would be useful to call Invoice.average_turnaround directly or Invoice.where(x: y).average_turnaround. Place all. in front of map.

class Invoice < ActiveRecord::Base
  ...
  def self.average_turnaround
    all.map(&:turnaround).inject(:+) / all.count
  end
end

Use average_turnaround using any collection.

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梦与时光遇 2024-09-21 04:21:06

您定义了一个类方法，该方法在类本身上调用。您需要的是关联扩展。该方法应该在您的客户端模型上定义，如下所示：

class Client < ActiveRecord::Base
  has_many :invoices do
    def average_turnaround
      return map(&:turnaround).inject(:+) / count
    end    
  end

You defined a class method, which is called on the class itself. What you need is an association extension. The method should be defined on your client model like this:

class Client < ActiveRecord::Base
  has_many :invoices do
    def average_turnaround
      return map(&:turnaround).inject(:+) / count
    end    
  end

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