Given a rake task that references both a namespaced and non-namespaced model:
namespace :thing do
task :thingo => :environment do
Klass.first.some_method
Namespaced::Klass.first.some_other_method
end
end
Using ruby 1.9.2, rails 3.0.9, and rake 0.9.2, this yields an exception, like so:
undefined method 'some_other_method' for #<Klass:0x007fcfafbaa6e0>
Two things:
Why doesn't rails return the proper namespacing in the rake environment (in a debugger session), but it does in a console session?
Why does changing the order of reference work? (That is, if the environment is already calling "Namespaced::Klass" as "Klass", then calling "Klass" should fail with undefined method 'some_method' for #<Klass:0x007fcfafbaa6e0> right?
By the way, I've tried ::Namespaced::Klass.first.some_other_method
If the answer isn't simple, I'll put together a test app - let me know! :-)
First, some background on metaphor shear - two different kinds of namespaces:
Although Rake Namepsaces and Ruby Namespaces share the word Namespace, they are separate concepts. Rake namespaces are just organizing containers for Rake Tasks, not Ruby namespaces/modules. So code inside your thing:thingo rake task is actually executing at the top-level Ruby namespace.
Second: If Klass is a single class not in a namespace, you can reference it directly. If the class exists as Foo::Klass then you'll need to use the fully-qualified Foo::Klass reference unless the scope of the reference is already within the Foo namespace.
Because Rake namespaces aren't Ruby modules, you are not in the context of a Ruby namespace within your task. This is why Klass.some_method works if Klass isn't in a module.
If this doesn't explain the question, please post the class definition for Klass including any module/namespace membership.
Related
I have a Document model in my Rails 4 app which starts like this:
class Document < ActiveRecord::Base
TYPES = [FileList, Article, VariantList, LinkedItemsList].collect(&:model_name)
...
end
The TYPES array contains a list of other models in my app and is used in a few places, for example to display a list of possible document types in one of my forms.
Now I'm writing a Rake task to automate some stuff and I get this error at line 2 in my Document model when I run the task:
NoMethodError: undefined method 'model_name' for Rake::FileList:Class
So apparently there's the Rake::FileList class which is being loaded first and I get a name conflict. Using ::FileList in my code doesn't help, I get the same error.
Any idea how to get around this without renaming my model?
UPDATE:
My Rake task definition looks like this:
namespace :store do
desc 'Some description'
task :my_task_name, [:a_parameter_name] => [:environment] do |t, args|
...
end
end
I think this is loading the environment correctly, as I'm calling (loading from DB) some other models before I get to Document and that is working correctly.
One think you can try is to give it an alias to FileList, at the end of you class definition:
class FileList < ActiveRecord::Base
...
end
FileListCopy = FileList
then in your rake access to FileListCopy.
When you're calling FileList from Document model, it tries to resolve this constant in the following order:
It tries to find the constant in the elements of the Module.nesting chain. In your case nesting is just [Document] and it does not contain FileList constant.
Then it tries to find constant in object's ancestors.
And finally the constant is looked up in Object.
Rake exposes its DSL globally by extending Object with Rake::DSL module. Thus, while using rake you're always getting FileList from the rake.
To overcome this issue you may move all your code into namespace. For example MyApp::FileList and MyApp::Document. In that case constant lookup algorithm will try to find constant in the elements of the nesting ([MyApp::Document, MyApp]). The second element of the nesting (MyApp) contain FileList constant. So, it would be resolved from MyApp module instead of Rake.
To avoid such kind of issues it's always a good idea to put your code into some namespace.
When working with ruby on rails, it is common to use terminal commands like rake db:migrate or rails g devise:install. But what exactly does the : in these commands mean? In rake db:migrate is migrate a parameter or something else?
You can think of the colon as a namespace. Somewhere within Rails there is a rake task file that looks similar to this:
namespace db
task :migrate do...
....
end
end
It's a way to group related tasks together and prevent them from colliding with other tasks. This way you could potentially have devise:migrate, db:migrate, foobar:migrate, etc.
Like Philip explained in his answer when using rake the colon defines the seperator between namespaces/tasks
When using rails g(enerate) it's basically the same. The difference is that Rails generators aren't defined with rake's DSL, instead they're classes.
But to answer your initial Questions: The Colon works as seperator, in both cases, that's it.
In the code the only thing what it's important for is splitting up the string:
https://github.com/rails/rails/blob/4-0-stable/railties/lib/rails/generators.rb#L124
You can find some more infos about generators and how to create your one ones (which definetley will help you understanding the mechanics behind it) in the official Ruby on Rails Guides
//EDIT
Ok, let's take a closer look at the generator lookup process:
First of all there is Rails::Generators.invoke
It receives the namespaces passed on the CLI and split's it up (using the colon)
names = namespace.to_s.split(':')
then it get's the according class by passing the last part of the passed namespace (the actual generator name) and the remaining part joined with a colon again (the namespace path, in our case it's devise) to Rails::Generators::Base.find_by_namespace
if klass = find_by_namespace(names.pop, names.any? && names.join(':'))
This method again will join the base (namespace path) and name (generator name) and push it to an array:
lookups = []
lookups << "#{base}:#{name}" if base
after that it calls Rails::Generators.lookup which will lookup the classes to invoke for the called generator:
lookup(lookups)
which will again will call Rails::Generators.namepaces_to_paths
There's no big magic in that method, it'll simply return an array of two possible source paths for the invoked generator in our case these two are "devise/install/install" and "devise/install".
Whereby those aren't the actual paths rails will check, they are only the part's of it that are depend on the namespace:generator construct.
The lookup method will now take those two, let's call them subpaths, and check for files to require at the following places:
rails/generators/devise/install/install_generator
generators/devise/install/install_generator
rails/generators/devise/install_generator
generators/devise/install_generator
in our case the second path is the desired file, rails require's it and through that the inherited (more about that callback callback on Rails::Generators::Base will get called since Devise::Generators::InstallGenerator inherits from it.
This will add the Class to the subclasses array of Rails::Generators which is mapped to an Hash which will have the format { namespace => klass } and so rails is finally able to get the desired Generator Class
klass = namespaces[namespace]
and start it
klass.start(args, config)
Found this post Include namespace in Rails 3.1 console but it doesn't seem to work.
The following lib/task defined and it works from the command line: rake namespace_name:task_name.
How to call a method method_name in namespace_name from within the console, without calling the task?
rails console
namespace_name::task_name
NameError: undefined local variable or method 'namespace_name' for main:Object
irb namespace_name
NameError: undefined local variable or method 'namespace_name' for main:Object
Working in Rails 3.07, Ubuntu.
If you want to call a method defined inside a .rake file you do something similar to what #Nate said, but instead of calling the raketask, call the method:
require 'rake'
Rake.load_rakefile 'lib/tasks/namespace_name.rake'
method_name(arg1, arg2)
It feels kind of strange that you don't need to specify the namespaces but I just tried this and it worked.
You're confusing two different kinds of "namespaces" - Ruby modules can perform the task of "namespacing" Ruby code; Rake namespaces are only used within Rake to categorize tasks, and they don't create a module namespace.
The page you linked only works with Ruby module namespaces.
If you want to call Rake tasks from the Rails console, it's a bit more involved...
require 'rake'
Rake.load_rakefile 'lib/tasks/namespace_name.rake'
Rake::Task['namespace_name:task_name'].invoke
Or just call it on the command line from within the Rails console -
%x[rake namespace_name:task_name]
This is a 2nd part to the following question:
Where to put model "utility" functions in Ruby on Rails
Problem is, I need access to these utility functions from a rake task as well. Using the accepted technique in in the other thread, I get an "undefined method" error when accessing my model from a rake task.
What is the best way to fix this?
Thanks
You probably need to define your rake task as dependent on the Rails environment:
task :my_task => :environment do
# Will load Rails stack before executing this block
MyModel.foo
end
The default behavior is to load almost nothing, so you won't have access to your models unless you ask for it.
I have a model, let's call it Foobar. I want to be able to run a cron job to update an attribute of all objects that are instances of Foobar. So, in pseudocode, it might be something like this:
Foobar.all.each do |foobar|
foobar.update_attributes({:my_attribute => 'updated'});
end
Now, let's say I wrap that in a class method called Foobar.run_update().
Calling Foobar.run_update() would work fine from the controller, or even from a view. But, what I want to do is run run_update() from the Rakefile so that I can tie it into a cron run. But, the Foobar class is not available to Rake when it is called from crontab.
How can I resolve that? How can I access the class methods of Foobars from Rake, when Rake is called from cron?
Thank you very much for your help.
By rake, if you mean a rake task then adding => :environment loads the rails environment for the task and you be able to call the Foobar.run_update method there. Like,
namespace :foobar do
task :update => :environment do
Foobar.run_update
end
end
And you should just be able to call rake foobar:update from the console and have it scheduled as a cronjob.
You can load up the Rails environment by requiring config/environment.rb:
ENV["RAILS_ENV"] ||= "production"
require '/where/your/rails/project/is/config/environment.rb'
In my Sinatra apps I typically have the file models/init.rb which requires Sequel, sets up my DB connection, and then uses require_relative to require all my model files. My main application then does require_relative "models/init".
With this setup any other script (including IRB) all I have to do is require the models/init.rb file myself, and I have full access to the same models and DB connection that the application has.