ruby-on-rails - 在 Rails 启动期间创建类的实例

Question

我试图在 Rails 加载时创建一个类的多个实例，并保持这些实例可用。 (我正在从 YAML 文件加载数据，但我已经抽象出这个问题的细节。)我有一个非 ActiveRecord 模型，它带有一个加载数据的 instantiate 类方法。当我从 config.after_initialize 和/或从自定义初始化程序调用 instantiate 时，实例已创建，但到 rails console 完成加载时，他们走了。我在哪里可以实例化数据，以便它在 Rails 控制台(和服务器)中可用？

# app/models/test.rb
class Test
  include ActiveModel::Model
  attr_accessor :name

  class << self
    include Enumerable

    def each
      ObjectSpace.each_object(self).each do |object|
        yield object
      end
      self
    end

    def find_by_name(input)
      find { |object| object.name.to_s == input.to_s }
    end

    def instantiate
      new(name: 'Alice')
      new(name: 'Bob')
    end
  end

  def initialize(*parameters)
    super(*parameters)
    freeze
  end

  delegate :to_s, to: :name
end


# config/application.rb
module MyApp
  class Application < Rails::Application
    config.after_initialize do
      p "Test instances before after_initialize: #{Test.count}"
      Test.instantiate
      p "Test instances after after_initialize: #{Test.count}"
    end
  end
end


# config/initializer/test_initializer.rb
p "Test instances before test_initializer: #{Test.count}"
Test.instantiate
p "Test instances after test_initializer: #{Test.count}"


$ rails console
"Test instances before test_initializer: 2"
"Test instances after test_initializer: 4"
"Test instances before after_initialize: 0"
"Test instances after after_initialize: 2"
Loading development environment (Rails 4.2.6)
irb(main):001:0> Test.count
=> 0
irb(main):002:0> Test.instantiate
=> #<Test:0x007fad2204d8b0 @name="Bob">
irb(main):003:0> Test.count
=> 2

Answer 1

Ruby 垃圾收集器从内存中删除实例。不存在引用新创建的实例的直接链接，因此 Ruby 认为它们是不必要的。

您可以通过添加来尝试:

module MyApp
  class Application < Rails::Application
    config.after_initialize do
      GC.disable # Disable garbage collector
      p "Test instances before after_initialize: #{Test.count}"
      Test.instantiate
      p "Test instances after after_initialize: #{Test.count}"
    end
  end
end

但是禁用垃圾收集器并不是一个好主意。如果您以某种方式引用实例，它们将不会被清除，并且它们将在启动后通过引用可用。