如何渴望将关联加载到实例变量中? [英] How to eager load associations into an instance variable?

问题描述

在模型中，我有:

class CalendarItem < Resource
  belongs_to :schedule

  has_many :people
  has_many :documents

  acts_as_list scope: :schedule, column: :visual_position

  validates :schedule, :title, presence: true
end

然后进入控制器:

class ScheduleController < ApplicationController
  def show
    @calendar_items = CalendarItem.where(schedule: @schedule).includes(:people, :documents)
  end

  ...
end

在视图中，我正在渲染带有react-rails的react_component(但这应该有所不同):

In the view I'm rendering a react_component with react-rails (but that should make any difference):

= react_component('CalendarItemsList', calendar_items: @calendar_items)

但是，它不会将关联数据传递给视图(react_component)，而只会传递给主模型.

However it does not pass the associated data to the view (react_component), only main model.

我以前在没有反应的前端上经历过这种情况，但也没有用.有什么问题吗?

I have experienced this before, with non-react front-end, and it didn't work either. What could be wrong?

推荐答案

问题不在于实例变量中的数据，而在于序列化.

The problem is not with the data in in the instance variable but with the serialisation.

react_component视图助手将在第二个参数(如果它不是字符串)上调用to_json方法.在您的情况下:{calendar_items: @calendar_items}.to_json，它可以递归工作，因此您要确保@calendar_items.to_json返回期望的JSON输出.您可以在rails console中使用@calendar_items.serializable_hash对其进行测试，它会返回一个哈希值，该哈希值对于人类来说更易读.

The react_component view helper will call the to_json method on the second argument if it is not a string. In your case: {calendar_items: @calendar_items}.to_json, which works recursively, so you want to make sure @calendar_items.to_json returns the expected JSON output. You can use @calendar_items.serializable_hash for testing it in the rails console, it returns a hash, which is more readable for humans.

或者您将数据序列化为字符串，然后将其提供给react_component.

Or you serialise your data into a string and feed the react_component with it.

我不知道Rails 5序列化，但它似乎与 ActiveModelSerializers 类似，因此您可以在序列化输出中包括这些关系，例如:@calendar_items.to_jso(include: [:documents]).在ActiveModelSerializers中，您可以为每个类指定一个序列化器，并指定它们之间的关系，这些关系可以自动包括在内.

I dont know Rails 5 serialization but it seems to be similar to ActiveModelSerializers so you can include the relationships in the serialised output like: @calendar_items.to_jso(include: [:documents]). In ActiveModelSerializers you can specify a serialiser to each class, and specify the relationships on them, those can be included automatically.

一个可行的解决方案可能是:

So one working solution could be:

def show
  calendar_items = CalendarItem.where(schedule: @schedule).includes(:people, :documents)
  @react_component_props = { calendar_items: calendar_items.to_json(include: [:people, :documents]) }
end

= react_component('CalendarItemsList', @react_component_props)

一个小技巧:您可以在CalendarItem模型上创建一个by_schedule范围，因此以后可以使用它:CalendarItem.by_schedule @schedule

A modest tip: you can create a by_schedule scope on the CalendarItem model, so later you can use it: CalendarItem.by_schedule @schedule

编辑

如果需要在视图中其他位置放置数据，则可以使用as_json方法:

If you need the data other places in the view then you can use the as_json method:

def show
  calendar_items_scope = CalendarItem.where(schedule: @schedule).includes(:people, :documents)
  @calendar_items = calendar_items_scope.as_json(include: [:people, :documents])
end

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