回报率：MyModel.descendants在第一次通话后视图返回[]？ [英] RoR: MyModel.descendants returns [] in a view after the first call?

问题描述

我要显示在视图中为MyModel子类的选择列表。它不工作呢，所以理智的检查，我包括这在我的观点：

I want to display a selection list of MyModel subclasses in a view. It's not working yet, so for sanity checking, I included this in my view:

<%= MyModel.descendants %>

在第一的时候，我渲染后重新启动服务器这个页面，它显示后裔的名单（有六个）。所有的以后的时候，它显示为空列表 [] 。

The first time I render this page after re-starting the server, it shows the list of descendants (there are six). All subsequent times, it shows up as an empty list [].

FWIW，我有我的初始化一个要求语句：

FWIW, I have a require statement in my initializers:

Dir[Rails.root.join("app/models/my_models/**/*.rb").to_s].each {|f| require f}

...我已经验证了他们得到必需的。

... and I've verified that they're getting required.

什么是@（$％＆放大器;？是怎么回事

What the @($%& is going on?

推荐答案

当您使用需要，即使你的 my_model.rb 被重新加载，内核不会要求你的子类 .RB 文件，因为它们已经被加载。你必须要经过导轨自动加载。

When you use require, even if your my_model.rb gets reloaded, the kernel won't require your subclasses .rb files because they have already been loaded. You'd have to go through rails autoload.

基本上，你的第一个要求，轨道自动加载为MyModel 从 my_model.rb ，然后要求 my_models / sub_model.rb 。该子模型类继承为MyModel ，其中填充的后裔阵列。 在你的下面的请求，不过，导轨自动加载为MyModel 试（嘿嘿，你是在开发模式），然后要求 my_models / sub_model.rb 了。但是这一次，内核知道它已经加载该文件，并不会再加载它。

Basically, on your first request, rails autoloads MyModel from my_model.rb, which then requires my_models/sub_model.rb. The SubModel class inherits MyModel, which populates the descendants array. On your following requests, though, rails autoloads MyModelagain (hey, you're in dev mode), which then requires my_models/sub_model.rb again. But this time, the kernel knows it had already loaded this file and won't load it again.

我一小时前就遇到了这个问题，这导致我​​到您的文章，并找到解决的办法。我们需要的是导轨自动加载的子类，每次你的主类调用。

I ran into this problem one hour ago, which lead me to your post, and to find a solution. What we need is rails to autoload subclasses everytime your main class is called.

下面是一个解决方案：

class MyModel
  Dir[File.join(File.dirname(__FILE__),"my_models","*.rb")].each do |f|
    MyModels.const_get(File.basename(f,'.rb').classify)
  end
end

这些线路很可能是类的外放。这应该是足够（这是对我来说），如果你只有在 my_models 文件，而不是在子目录中。如果你有一些（例如 MyModels ::汽车::福特，你可能需要把同样的东西在的子模块（在 my_models /car.rb ）。

These lines could probably be put outside of the class. That should be enough (it is for me) if you only have files in my_models and not in subdirectories. If you have some (for example MyModels::Car::Ford, you may need to put the same kind of stuff in the submodules (in my_models/car.rb).

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