How to call methods of an external class in Ruby - ruby-on-rails

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?

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.

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.

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?

Related

How to use cattr_accessor to define config in a Rails initializer

Given the following class (this is the actual class there is no other code)
class PageRepo
cattr_accessor :root_path
end
and initializer file
PageRepo.root_path = Rails.root.join("content")
When I run
rails console
PageRepo.root_path
=> PageRepo.root_path
=> #<Pathname:/Users/blah/my_rails_app/content/pages>
However when I try to access this in my rails controller the root_path value is nil. (I've inspected this with web_console.)
No other class subclasses or is a parent of the PageRepo class and I'm not setting the root_path to nil anywhere at class level or instance level after the initializer stage. I have restarted spring and my server multiple times to no avail.
Is there something I'm not aware of when it comes to either Rails initializers or cattr_accessor?
Update
I'd like to set the path like this because throughout my code I will be initialising a PageRepo instance and the path will not change. However, it may change across different environments. I.e. in development it the path will be different than that of the test and production environments. Whilst I could just do
def initialize
#root_path = ENV['ROOT_PATH']
end
I'd prefer to not force the programmer to use ENV VARS to do this and hence my attempt above.
My solution would be just using a class method
class PageRepo
self.root_path
Rails.root.join("content")
end
end
PageRepo.root_path would return #<Pathname:/Users/blah/my_rails_app/content/pages>.
You want to have #<Pathname:/Users/blah/my_rails_app/content/pages>? or this depends on the action?
I believe your initializer is not working
an interesting post, what you are trying to achieve is writing something like this in the class initializer or constructor
class PageRepo
self.initialize
self.root_path = Rails.root.join("content")
end
end
but I never saw self.initialize being used with rails. so I believe the first approach is better.

RAILS 4.1.4: My class in the lib folder loads as a module?

I've written a tiny game in the form of a Class. I've placed that file in the lib folder and I've set the appropriate loader in config/application.rb . But when I try to call Game.new in my controller it says undefined method 'new' for Game:Module. I want to be very clear THIS IS NOT A MODULE. Why the heck is it treating my class as a module? How can I fix it?
class Game
def initialize
end
end
See... this is a class with the .new method. It loads fine in IRB, but not in Rails.
I got it. It turns out I had named the class the same name as my rails project name. So it would only accept a module for that name. I renamed the class and file and now I'm good to go.

Uninitialized constant trying to reopen a Class

I am using a plugin in Rails, and I call its methods without problems:
plugin_module::class_inside_module.method_a(...)
I want to re-open the class_inside_module and add a new method, I tried in many different ways. I can't figure out why in this way doesn't work:
class plugin_module::class_inside_module
def new_method
puts 'new method'
end
end
I get the error: uninitialized constant plugin_module, but how is possible if I can call without problem plugin_module::class_inside_module.any_methods ?
Do you know why I get that error ? why "uninitialized constant" ? (it is a class declaration :-O )
Do you have any ideas how I can add a new methods in a class inside a module (that is part of a plugin) ?
Thank you,
Alessandro
If you have written your class and module-names like you did, so plugin_module instead of PluginModule this is against ruby/rails standards, and rails will not be able to automatically find the class and module.
If you write something like
module MyModule
class MyClass
end
end
Rails will expect this file to be located in lib\my_module\my_class.
But this can always easily be overwritten by explicitly doing a require.
So in your case, when you write
module plugin_module::class_inside_module
Rails will not know where to find the module plugin_module.
This way of writing only works if module plugin_module is previously defined (and loaded).
So either add the correct require, or rename your modules to standard rails naming, or write it as follows:
module plugin_module
class class_inside_module
This way will also work, because now the order no longer matters.
If the module is not known yet, this will define the module as well.
Either you are re-opening the class, or you define it first (and the actual definition will actually reopen it).
Hope this helps.
Have you tried reopening the module that's wrapping the class, rather than relying on ::?
module plugin_module
class class_inside_module
def new_method
puts 'new_method'
end
end
end
By the way, you know that the proper name for modules and classes is use CamelCase with a capital first letter?
module PluginModule
class ClassInsideModule
def new_method
puts 'new_method'
end
end
end

Using class function from the lib directory in rails

I am creating a rails3 application and I want to create a class that handles string formatting, so I made a class called FormatUtilites.rb in the lib directory but whenever I try calling it from somewhere else in my app I get this error:
ActionView::Template::Error (uninitialized constant ActionView::CompiledTemplates::FormatUtilities)
So it thinks its a constant and not a class method, which is how it is defined. Any ideas?
class FormatUtilities
def self.slugify(name)
name.downcase.gsub(/\s|\W|\D/, "")
end
end
Thanks!
Turns out rails3 stop autoloading the lib directory. I have no idea why they did it, but they did. Just needed to add it to the autoload in the application.rb
thanks anyways!
Classes are constants in Ruby, besides also being classes. Probably you just need to do "require format_utilities"
You need to add:
# in config/application.rb
config.autoload_paths = %W(#{config.root}/lib
The name of your file should be format_utilities.rb for autoload to work.
In your particular case i would use a different aproach. Instead of creating a class with static functions i would create a module named FormattingHelper in app/helpers/formatting_helper.rb like this.
class FormattingHelper
def slugify(name)
name.downcase.gsub(/\s|\W|\D/, "")
end
end
Then in ApplcationController or in a specific controller i would add:
class ApplicationController < ActionController::Base
helper :formatting
end
If you want rails to automatically load this file when it boots, you will need to name your file format_utilities.rb. The next time you restart your server or console, you should be able to do FormatUtilities.slugify("name")

Ruby Module Include Question

I have a CommonFunctions Module inside the lib/ folder. I have a Question Model, which includes the CommonFunctions module. Now I am trying to access the favorite function of the CommonFunctions like Question.favorite. But I am getting NoMethodError. I have included the code. Can anyone please tell me where I am doing the mistake
Error
NoMethodError: undefined method `favorite' for Class:0x00000100e11508
Inside lib/CommonFunctions.rb
module CommonFunctions
def favorite(object_id)
end
end
Inside app/models/Question.rb
require 'lib/CommonFunctions.rb'
class Question
extend CommonFunctions
end
I am executing the following code from the script/console
Question.favorite(1)
Thanks
This was a duplicate of How do I properly include a module and call module functions from my Rails model?
Your code is correct. Make sure you have the current version of the classes loaded in the console (try reload!).
As a sidenote: if you rename CommonFunctions.rb to common_functions.rb, it will be autoloaded by rails and you don't need the require.
The module method is an instance method when you want it to be a class method. Use the code below instead
module CommonFunctions
def self.favorite(object_id)
end
end
Using the word "self" defines the method as a class method (or static)

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