ruby 将字符串中的类名转换为实际类
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ruby convert class name in string to actual class
提问by unsorted
How do I call a class from a string containing that class name inside of it? (I guess I could do case/when but that seems ugly.)
如何从包含该类名的字符串中调用类？（我想我可以做 case/when 但这看起来很难看。）
The reason I ask is because I'm using the acts_as_commentableplugin, among others, and these store the commentable_type as a column. I want to be able to call whatever particular commentable class to do a find(commentable_id)on it.
我问的原因是因为我正在使用acts_as_commentable插件等，这些插件将 commentable_type 存储为一列。我希望能够调用任何特定的可评论类来find(commentable_id)对其进行处理。
Thanks.
谢谢。
回答by Jamie Wong
I think what you want is constantize
我想你想要的是 constantize
That's an RoR construct. I don't know if there's one for ruby core
这是一个 RoR 结构。不知道有没有ruby core的
回答by jtbandes
"Object".constantize # => Object
回答by user664833
Given a string, first call classifyto create a class name (still a string), then call constantizeto try to find and return the class name constant (note that class names are constants).
给定一个字符串，首先调用classify创建一个类名（仍然是一个字符串），然后调用constantize尝试查找并返回类名constant（注意类名是constants）。
some_string.classify.constantize
回答by Edgar Ortega
I know this is an old question but I just want to leave this note, it may be helpful for others.
我知道这是一个老问题，但我只想留下这个笔记，它可能对其他人有帮助。
In plain Ruby, Module.const_getcan find nested constants. For instance, having the following structure:
在普通 Ruby 中，Module.const_get可以找到嵌套常量。例如，具有以下结构：
module MyModule
module MySubmodule
class MyModel
end
end
end
You can use it as follows:
您可以按如下方式使用它：
Module.const_get("MyModule::MySubmodule::MyModel")
MyModule.const_get("MySubmodule")
MyModule::MySubmodule.const_get("MyModel")
回答by skalee
When ActiveSupport is available (e.g. in Rails): String#constantizeor String#safe_constantize, that is "ClassName".constantize.
当 ActiveSupport 可用时（例如在 Rails 中）：String#constantize或String#safe_constantize，即"ClassName".constantize.
In pure Ruby: Module#const_get, typically Object.const_get("ClassName").
在纯 Ruby 中：Module#const_get，通常是Object.const_get("ClassName").
In recent rubies, both work with constants nested in modules, like in Object.const_get("Outer::Inner").
在最近的 rubies 中，两者都使用嵌套在模块中的常量，例如 in Object.const_get("Outer::Inner")。
回答by SSR
If you want to convert string to actuall class name to access model or any other class
如果要将字符串转换为实际类名以访问模型或任何其他类
str = "group class"
> str.camelize.constantize 'or'
> str.classify.constantize 'or'
> str.titleize.constantize
Example :
def call_me(str)
str.titleize.gsub(" ","").constantize.all
end
Call method : call_me("group class")
Result:
GroupClass Load (0.7ms) SELECT `group_classes`.* FROM `group_classes`
