英文:
Deduce controller name from namespaced string
问题
在我的Rails代码库中，我使用了以下代码：
Rails.application.routes.recognize_path(request.referer)
我的目标是获取:controller键的类对象。到目前为止，我只能得到类似于my/namespace/posts的东西。
然而，真正的类名是My::Namespace::PostsController。有没有自动推断类名的方法？否则，有什么更优雅的方法可以实现这一目标？
英文:
At some point in my Rails codebase I'm using the following:
Rails.application.routes.recognize_path(request.referer)
My goal is to get the class object of the :controller key.
So far I've only gotten to something like this: my/namespace/posts.
The true class however is My::Namespace::PostsController. Is there any way to automatically deduce the class name?
Otherwize, what't the most elegant way to get to that?
答案1
得分: 3
@zakariah提到了ActionDispatch::Request#controller_class，它看起来应该可以正常工作，前提是params[:controller]是一个String，尽管我没有测试过：
params = {controller: '/my/namespace/posts'}
ActionDispatch::Request.new({}).controller_class_for(params[:controller])
#=> My::Namespace::PostsController
request.controller_class # 理论上
#=> My::Namespace::PostsController
然而，如果控制器不存在，这将引发错误。
话虽如此，根据您当前的实现，您已经成功获取了字符串"my/namespace/posts"，这意味着您已经完成了90%的工作。
要将其转换为所需的控制器名称实际上非常简单：
str = "my/namespace/posts"
controller_name = str.camelize << "Controller"
#=> "::My::Namespace::PostsController"
controller_name.safe_constantize
#=> ::My::Namespace::PostsController
这实际上是AbstractController::Base#controller_path的简单反转，它使用了underscore。
正如文档中所提到的：
ActiveSupport::Inflector::camelize
[
camelize] 还将'/'转换为'::'，这对于将路径转换为命名空间很有用...
重要说明:
...作为一个经验法则，您可以认为
camelize是underscore的反义词，尽管有些情况不成立：
camelize(underscore('SSLError')) # => "SslError"
因此，如果需要，您需要确保设置了正确的词形规则。
我选择使用safe_constantize，如果常量不存在，它将返回nil。这允许您以更符合惯例的方式处理这些问题（缺少常量），例如：
controller_name.safe_constantize || DefaultContoller
英文:
@zakariah mentioned ActionDispatch::Request#controller_class which appears like it should work provided that params[:controller] is a String, although I have not tested it:
params = {controller: '/my/namespace/posts'}
ActionDispatch::Request.new({}).controller_class_for(params[:controller])
#=> My::Namespace::PostsController
request.controller_class # in theory
#=> My::Namespace::PostsController
however this will raise an error if the controller does not exist.
That being said based on your current implementation, you have managed to get to the String "my/namespace/posts", which means you are 90% of the way there.
To convert this to the desired controller name is actually fairly simple:
str = "my/namespace/posts"
controller_name = str.camelize << "Controller"
#=> "::My::Namespace::PostsContoller"
contoller_name.safe_constantize
#=> ::My::Namespace::PostsContoller
This is a simple inversion of AbstractController::Base#controller_path, which uses underscore.
As mentioned in the docs:
ActiveSupport::Inflector::camelize
> [camelize] Also converts '/' to '::' which is useful for converting paths to namespaces....
Important Note:
> ...As a rule of thumb you can think of camelize as the inverse of underscore, though there are cases where that does not hold:
>
>camelize(underscore('SSLError')) # => "SslError"
So you will need to ensure that the proper inflections are setup if needed in your application.
I chose to use safe_constantize which will return nil if the constant does not exist. This allows you to handle these issues (missing constants) in a more idiomatic fashion e.g.
controller_name.safe_constantize || DefaultContoller
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