I've generated an object via a ruby gem (Koala) and I've written a few modules with helper methods. What do I need to do in order to be able to use the methods within the modules on the object?
If I, model_object = Model.new, model_object will have access to all the instance variables but object does not (see below).
Ruby 2.1, Rails 4.1
config/application.rb - Autoloading modules in folder
config.autoload_paths << Rails.root.join('lib/module_folder')
Model
class Model < ActiveRecord::Base
include Module
include Module::Module2
include Module::Module3
def self.create_account(token)
object = Module.module_class_method(token) #this works and generates the Koala object
ERROR: object.module2_instance_method # Error: NoMethodError Exception: undefined method
end
end
Module
module Module
extend ActiveSupport::Concern
end
Module2
module Module
module Module2
def module2_instance_method
end
end
end
SOLVED MYSELF
- the issue was the include statements being within the class, if I moved them outside it worked.
I believe if you include your modules somewhere under the app/ directory - they will be included automatically. Otherwise, you actually have to require them in your rails code explicitly with a require statement
Without seeing the actual code, I think the problem with Module2 in your code snippet is the self. method.
Because you are calling module2_instance_method on an instance of your object, the method in the module cannot have the self. because that designates a class method and, as such, would have to be called as Module::Module2.module2_instance_but_not_really_because_I_am_a_class_method.
I believe if you change def self.module2_instance_method ... end to def module2_instance_method ... end, you should no longer receive the NoMethodError exception.
Apologies if I've misread or misunderstand the OP.
Moved the include statements from inside to above the class declaration and all methods began to work. My assumption is that when they are within the statement they are only available to objects of that class.
Related
In Rails, how do you use a specific method from a module. For eg,
# ./app/controllers/my_controller.rb
class MyController < ApplicationController
include MyModule
def action
MyModule.a_method
end
private
def a_method
...
end
end
# ------------------------------------------------ #
# ./app/helpers/my_module.rb
module MyModule
def a_method
...
end
end
MyController includes MyModule. And in action ,I want to use MyModule.a_method (Please note I also have a private a_method in MyController and I don't want to use this.)
Things I've tried :
1) Defining the method in the module as self.
def self.a_method
end
2) Using the :: notation in controller (MyModule::a_method)
The error that I keep getting is
Undefined method:a_method for MyModule:module
For now, I've resorted to using a different name for the modules method. But I'd like to know how to namespace the function with either the Module:: or Module. notation
[UPDATE - 11/24/2014]
adding file structure in code, since Rails heavily relies on convention.
So I am not really sure what you are trying to accomplish with your module but a quick solution to get it working is below.
Move my_module.rb out of helpers and into lib/my_module.rb. The helpers directory is for methods that you use in your views. The convention is to utilize helpers that are namespaced after their respective controller or the application_helper.rb for global methods for your views. Not sure if that's what you are trying to accomplish with your module but wanted to throw that out there.
Create an initializer (you can all it whatever) in config/initializers/custom_modules.rb and add require 'my_module'
Update the a_method back to be self.a_method
You can now call MyModule.a_method in your app
Don't forget to restart your server for changes to lib/my_module.rb to take effect.
Also, a lot of people reference this post by Yehuda Katz as guidance on where to store code for your app. Thought it might be a helpful reference.
if you include MyModule into MyController, all the "instance methods" of the first will be mixed-in into the 2nd.
So if you only want to call MyModule.a_method, no need to include your module.
Then you'd want to require (or better autoload) your module before using it. To do so place it in controllers/concerns/my_module.rb, rails (4 at least) should autoload it, otherwise require its file in an intializer
# my_module.rb
module MyModule
def self.a_method
...
end
end
should work, but doing
# my_module.rb
module MyModule
extend self
def a_method
...
end
end
is more clean to me. You'd like to have a look to rails active support concern to understand the "rails way" on this topic.
I have a /lib/custom
inside I have custom.rb and custom_page.rb
custom.rb
require 'custom_page.rb'
module Custom
def self.name(params)
# logic
end
end
I've added in application.rb config.autoload_paths += %W(#{config.root}/lib)
I can't seem to call in my controllers to Custom.name(params)
NoMethodError: undefined method `name' for Custom:Module
I've tried with define the method as def Custom.name, using class << self and method_function :name yet nothing helps..
Am I missing something?
It's because of the Rails naming convention. In your rails console, try
irb(main):001:0> Custom::Custom
LoadError: Expected lib/custom/custom.rb to define Custom::Custom
Rais expects you do define module Custom::Custom (not module Custom) in lib/custom/custom.rb.
Rails sees a folder lib/custom and created an empty module Custom (doesn't respond to name method) based on convention, if you want to define module Custom, you have to write a file lib/custom.rb
The convention is
lib/custom.rb #define module Custom
lib/custom/deeper.rb #define module Custom::Deeper
lib/empty_folder/ # rails provides you an empty module EmptyFolder
BTW you don't have to require 'custom_page' in your custom.rb, if Rails sees CustomPage in your code, it will try to load the class definition file based on naming convention, given that your custom_page.rb file path follows the convention.
You can also use ActiveSupport::Concern to extend both class and instance methods. In the module just to this:
module Custom
extend ActiveSupport::Concern
included do
# everything but the class methods go here
end
module ClassMethods
# define class methods here
def name(params)
#logic
end
end
end
I have a module called Sms that I'm defining in lib/sms.rb. Within it, I have a method called Sms.chunk that uses the method word_wrap. This is part of the TextHelper library, so I am including it at the beginning of the module with include ActionView::Helpers::TextHelper:
module Sms
include ActionView::Helpers::TextHelper
def Sms.chunk
...
word_wrap
...
I am requiring this module during initialization with the line require "sms" in config/initializers/additional_libs.rb
I also have a Grape API class called TWILIO_API where I want to call Sms.chunk. However, when I do, I get undefined methodword_wrap' for Sms:Module`. I have tried including the TextHelper library in the TWILIO_API class itself, and various other ways of including it, but have had no success.
What am I doing wrong here?
The problem is that wrap_word is an instance method , and you're invoking it from a class method Sms.chunk. Make it an instance method by dropping the Sms. part. For instance, the following works:
require 'action_view'
class Test
include ActionView::Helpers::TextHelper
def test_method
word_wrap('Once upon a time')
end
end
o = Test.new
p o.test_method # "Once upon a time"
Ok so I am using some module/lib/plugin (not sure of the exact name), let's say its a authentication/authorization plugin like: http://github.com/technoweenie/restful-authentication
class HomeController < ApplicationController
some_module_name_here
end
Now just from adding the code above 'some_module_name_here', I can access to methods from that module.
What is that line of code doing that gives me access to methods/objects from the module?
Is that declaring a variable like in say java/c#:
public SomeModule _someModule;
I know that plugins/modules basically extend the class under the covers, but how does it do this with a single line of code?
Is it called in the constructor somehow?
When you create a ruby plugin, and load it into the rails app via environment.rb, bundler, or a require call, the methods are loaded as "modules" that can be called. The ones that act like you're talking about will have an extra method called acts_as_list or something similar. All that method does is include the methods of the module into the class where that line was called.
Here's an example, which you could include in your app's lib folder and play with:
module Bellmyer
module Pointless
def self.included(base)
base.extend PointlessMethods
end
module PointlessMethods
def acts_as_pointless
unless included_modules.include? InstanceMethods
extend ClassMethods
include InstanceMethods
end
end
end
module ClassMethods
def pointless_class?
true
end
end
module InstanceMethods
def pointless_instance?
true
end
end
end
end
The module is available to any ruby class in your app, but the methods don't actually get loaded until you call acts_as_pointless, which then includes and extends your class with the methods listed. Only the acts_as_pointless method is immediately available to the model. This is the standard pattern for an ActiveRecord plugin.
That's not how it works.
When the plugin or gem is loaded it adds a class method to, in this case, ApplicationController named some_module_name. When you call that methods, a bunch of other class and instance methods are included.
Check out your favourite gem or plugin to see how they do it exactly.
I'm working on a Rails app and am looking to include some functionality from "Getting the Hostname or IP in Ruby on Rails" that I asked.
I'm having problems getting it to work. I was under the impression that I should just make a file in the lib directory, so I named it 'get_ip.rb', with the contents:
require 'socket'
module GetIP
def local_ip
orig, Socket.do_not_reverse_lookup = Socket.do_not_reverse_lookup, true # turn off reverse DNS resolution temporarily
UDPSocket.open do |s|
s.connect '64.233.187.99', 1
s.addr.last
end
ensure
Socket.do_not_reverse_lookup = orig
end
end
I had also tried defining GetIP as a class but when I do the usual ruby script/console, I'm not able to use the local_ip method at all. Any ideas?
require will load a file. If that file contains any class/module definitions, then your other code will now be able to use them. If the file just contains code which is not in any modules, it will get run as if it were in the same place as your 'require' call (like PHP include)
include is to do with modules.
It takes all the methods in the module, and adds them to your class. Like this:
class Orig
end
Orig.new.first_method # no such method
module MyModule
def first_method
end
end
class Orig
include MyModule
end
Orig.new.first_method # will now run first_method as it's been added.
There's also extend which works like include does, but instead of adding the methods as instance methods, adds them as class methods, like this:
Note above, how when I wanted to access first_method, I created a new object of Orig class. That's what I mean by instance method.
class SecondClass
extend MyModule
end
SecondClass.first_method # will call first_method
Note that in this example I'm not making any new objects, just calling the method directly on the class, as if it had been defined as self.first_method all along.
So there you go :-)
You haven't described how you're trying to use the method, so I apologize in advance if this is stuff you already know.
The methods on a module never come into use unless the module is included into a class. Instance methods on a class require there to be an instance of the class. You probably want a class method instead. And the file itself should be loaded, generally through the require statement.
If the following code is in the file getip.rb,
require 'socket'
class GetIP
def self.local_ip
orig, Socket.do_not_reverse_lookup = Socket.do_not_reverse_lookup, true
UDPSocket.open do |s|
s.connect '64.233.187.99', 1
s.addr.last
end
ensure
Socket.do_not_reverse_lookup = orig
end
end
Then you should be able to run it by saying,
require 'getip'
GetIP.local_ip
require and include are two different things.
require is to strictly load a file once from a load path. The loadpath is a string and this is the key used to determine if the file has already been loaded.
include is used to "mix-in" modules into other classes. include is called on a module and the module methods are included as instance methods on the class.
module MixInMethods
def mixed_in_method
"I'm a part of #{self.class}"
end
end
class SampleClass
include MixInMethods
end
mixin_class = SampleClass.new
puts my_class.mixed_in_method # >> I'm a part of SampleClass
But many times the module you want to mix in is not in the same file as the target class. So you do a require 'module_file_name' and then inside the class you do an include module.