Rails：在具有警告的子文件夹中组织模型：B :: A引用的顶级常量A

问题描述

今天，我决定重组大量与用户相关的模型，但我遇到了问题。

Today I decided to reorganize big amount of user related models and I'm having a problem with it.

在拥有这样的结构之前：

Before I had such structure:

app/models/user.rb
app/models/user_info.rb
app/models/user_file.rb
...

所以我移动了所有 user _ 将模型复制到用户子文件夹，如下所示：

So I moved all user_ models to user subfolder like this:

app/models/user.rb
app/models/user/info.rb
app/models/user/file.rb
...

并将其定义更改为

class User::Info < ActiveRecord::Base
class User::File < ActiveRecord::Base
...

User 模型未更改（关联除外）。

User model wasn't changed (except associations).

除 User :: File 之外，其他所有功能都正常模型。当我尝试访问此模型时，出现以下错误：

Everything works fine except User::File model. When i'm trying to access this model i get the following error:

warning: toplevel constant File referenced by User::File

并确实返回标准的ruby File类。

and indeed it returns standard ruby File class.

我在做什么错了？

UPD1：

root# rails c
Loading development environment (Rails 3.2.13)
2.0.0p195 :001 > User::File
(irb):1: warning: toplevel constant File referenced by User::File
 => File
2.0.0p195 :002 > User::Info
 => User::Info(...)

UPD2：

2.0.0p195 :001 > User::SomeModel
NameError: uninitialized constant User::SomeModel
2.0.0p195 :002 > User::IO
(irb):2: warning: toplevel constant IO referenced by User::IO
 => IO 
2.0.0p195 :003 > User::Kernel
(irb):3: warning: toplevel constant Kernel referenced by User::Kernel
 => Kernel 

我的应用程序没有任何IO或内核类，除了ruby默认。

My app doesn't have any IO or Kernel classes, except ruby default.

UPD3：

# app/models/user.rb
class User < ActiveRecord::Base
  has_many :files, class_name: 'User::File'
  ..
end

# app/models/user/file.rb
class User::File < ActiveRecord::Base
  belongs_to :user
  # some validations, nothing serious
end

推荐答案

更新：今年的圣诞节礼物是Ruby 2.5.0发行版，该错误不再发生。使用Ruby 2.5+，您将得到所需的常数或错误。对于较旧的Ruby版本，请继续阅读：

Update: This years Christmas present was the release of Ruby 2.5.0 with which this error won't happen anymore. With Ruby 2.5+ you will either get the constant you asked for or an error. For older Ruby versions read on:

您的 User :: File 类未加载。您必须要求它（例如在 user.rb 中）。

Your User::File class is not loaded. You have to require it (e.g. in user.rb).

当ruby / rails看到 User :: Info 并对其进行评估（简化；仅定义了 User ）。

The following happens when ruby/rails sees User::Info and evaluates it (simplified; only User is defined yet).

• 检查是否定义了 User :: Info -尚未（尚未）


• 检查是否定义了 Info -（尚未）


• 未初始化的常量->用魔力找到 user / info.rb 文件并要求它


• 返回 User :: Info

• check if User::Info is defined - it is not (yet)
• check if Info is defined - it is not (yet)
• uninitialized constant -> do rails magic to find the user/info.rb file and require it
• return User::Info

现在让 User再做一次： ：File

• 检查是否 User :: File 已定义-还没有（


• 检查是否已定义 File -是因为（因为ruby具有内置的 File 类）！


• 发出警告，因为我们被要求输入 User :: File 但得到了 :: File


• 返回 :: File

• check if User::File is defined - it is not (yet)
• check if File is defined - it is (because ruby has a built in File class)!
• produce a warning, because we've been asked for User::File but got ::File
• return ::File

我们观察到自动需要（尚未）未知常数的文件的rails魔术不适用于 User :: File ，因为文件是未知的。

We observe that the rails magic, that automatically requires files for (yet) unknown constants, does not work for User::File because File is not unknown.

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