当我只知道集合名称时，如何使用 Mongoid 动态调用模型？

Posted 2023-02-16

【中文标题】当我只知道集合名称时，如何使用 Mongoid 动态调用模型？

【英文标题】：How can I dynamically call a Model using Mongoid when I only know the collection name?

【发布时间】：2021-08-25 20:09:00

【问题描述】：

假设我有 20 多个模型，其中一个称为 Job

module API
  class Job
    include Mongoid::Document
    # ...

    store_in collection: :jobs

    # ...
  end
end

我正在处理一些 HTTP webhook，我正在指定系统管理员想要订阅更新的集合。

也就是说，我会知道集合叫jobs

known_info =  db_name: 'x', collection: 'jobs', id: '6095d84c5be78a26cc9d837b' 

## this is the normally way one would query jobs, but I want to mimic it
## dynamically not using the Module name
API::Job.find(known_info[:id])

## a second way that will NOT work,
## this evades all API code that I have written, I need to use my ruby code in the
## model with access to the class functions
document = nil
Mongoid.default_client.collections.each do |collection|
  next unless collection.namespace == "#known_info[:db_name].#known_info[:collection]"

  document = collection.find(_id: known_info[:id]).limit(1).first
end

## this will return the record from the database,
## but it will not send it through the model, its just the raw database value
pp document =>
"_id"=>BSON::ObjectId('6095d84c5be78a26cc9d837b'),
 ...

【问题讨论】：

ruby-on-rails 是否参与其中？如果ActiveSupport 可用，这会极大地改变答案。

您不能调用模型，因为它不是方法。如果您还有其他问题，请进行相应编辑。

你错了，我能弄明白。 @D.SM

@engineersmnky 没有轨道

【参考方案1】：

我能够通过执行以下操作来弄清楚。

使用包装模型的命名空间，您可以查询常量并缩小范围

known_info =  db_name: 'x', collection: 'jobs', id: '6095d84c5be78a26cc9d837b' 
document = nil
API.constants.each do |constant|
  module_class = API.const_get(constant)
  ## skip of the constant is not a class
  next unless module_class.is_a?(Class)
  ## skip if the class does not have a method called "collection_name"
  next unless module_class.respond_to?(:collection_name)
  ## skip if the collection does not match the known collection
  next unless module_class.collection_name.to_s == known_info[:collection]

  document = module_class.find(known_info[:id])
end

p document

## success!