如何在Ruby中调用外部类的方法

Question

I have a file under /lib with its own method.

# lib/file.rb
class File < ApplicationController
  def my_method
    ...
  end
end

However I can't reach the method through the console

ruby-1.9.2-p290 :044 > File.my_method
NoMethodError: undefined method `my_method' for File:Class

Any idea how?

Answer 1

my_method is an instance method of the File class. It means that you can call it only on the instance of the File class.

file = File.new
file.my_method

You can declare my_method as class method using def self.my_method syntax.

class File < ApplicationController
  def self.my_method
    ...
  end
end

File.my_method

But in class methods you can't use instance variables of the File object.

Answer 2

You're trying to call my_method as a class method, but you've defined it as an instance method.

You should either define it as def self.my_method , or create an instance of the controller to call it as an instance method.

In addition, you are going to run into problems for a couple of reasons - (1) Rails expects controllers to be named like FilesController , and (2) File is a class in the standard library. I would encourage you to change the class name to FilesController , and rename the file itself to files_controller.rb to prevent both issues.

Answer 3

Well... there are several interesting things going on with this example. The first would be that this class name is call File which is already defined in Ruby.

That is most likely why when you are in the console you didn't get an undefined class error. Since my_method is not defined on Ruby's File class, this is why you are seeing undefined method.

Now to your question. I would try naming your class something different first and trying again from lib . I believe it should be loaded by default again with the rails environment. For a version or two that functionality was taken out but I want to say it's back in. If not, just go into your config/application.rb file and look for a declaration along the lines of config.autoload_paths . Add the lib directory there and you should be good to go.

Lastly, is there a reason you want a controller in lib ?