252

I am trying to create a custom rake task, but it seems I dont have access to my models. I thought this was something implicitly included with rails task.

I have the following code in lib/tasks/test.rake:

namespace :test do
  task :new_task do
    puts Parent.all.inspect
  end
end

And here is what my parent model looks like:

class Parent < ActiveRecord::Base
  has_many :children
end

It's a pretty simple example, but I get the following error:

/> rake test:new_task
(in /Users/arash/Documents/dev/soft_deletes)
rake aborted!
uninitialized constant Parent

(See full trace by running task with --trace)

Any ideas? Thanks

John Topley
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gmoniey
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6 Answers6

435

Figured it out, the task should look like:

namespace :test do
  task :new_task => :environment do
    puts Parent.all.inspect
  end
end

Notice the => :environment dependency added to the task

New Alexandria
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gmoniey
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    what does this syntax mean? it's assigning `new_task` to the current environment? what is the current value of `:environment`? google is not helping. – Scott Coates Oct 18 '12 at 02:29
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    @scoarescoare :environment here is the dependency, so when running `new_task`, load the environment (load your models) first, and then run new_task. – bigpotato Jan 30 '13 at 16:16
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    @scoarescoare you can check [custom rake doc](http://guides.rubyonrails.org/command_line.html#custom-rake-tasks),the first example will tell you – lazybios Mar 29 '15 at 15:37
  • how to achieve same thing in Sinatra ? – AMBasra Aug 19 '15 at 21:30
  • model name has to follow with all and it does not work without it like TodoList.all.each not TodoList.each idk why it seems working? – Kick Buttowski Jul 04 '18 at 02:08
  • why is creating a namespace required? I wrote a rake task without namespace and I could not access records from my database. – Masroor Nov 23 '20 at 14:21
17

you might need to require your configuration (which should specify all your required models etc)

eg:

require 'config/environment'

alternatively you can just require each seperately, but you might have environment issues AR not set up etc)

Luke Schafer
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    This will work, but it will break rake in general! After adding this change, try rake -T without a DB available. rake -T should happily provide a list of rake tasks without needing access to the DB! – irkenInvader Sep 15 '10 at 21:42
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    After doing this you will find that any other rake tasks that requires initializing the application (i.e. rake assets:precompile) will fail with "rake aborted! Application has been already initialized". – Brent Apr 10 '14 at 20:08
14

When you begin writing your rake tasks, use a generator to stub them out for you.

For example:

rails g task my_tasks task_one task_two task_three

You'll get a stub created in lib/tasks called my_tasks.rake (obviously use your own namespace.) Which will look like this:

namespace :my_tasks do

  desc "TODO"
  task :task_one => :environment do 
  end  

  desc "TODO"
  task :task_two => :environment do 
  end  

  desc "TODO"
  task :task_three => :environment do 
  end  

end

All your rails models etc. will be available for the current environment from within each task block, unless you're using the production environment, in which case you need to require the specific models you want to use. Do this within the body of the task. (IIRC this varies between different versions of Rails.)

ocodo
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    Couldn't you just say that `environment` is required as a dependency and then say the syntax rather than encouraging the OP to rely on "magic" utilities that don't even use any magic? – Joshua Grosso Reinstate CMs Feb 04 '16 at 18:14
7

With the new ruby hash syntax (Ruby 1.9) the environment will be added like this to the rake task: 

namespace :test do
  task new_task: :environment do
    puts Parent.all.inspect
  end
end
apadana
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6

Generate task using below command (namespace with task name):

rails g task test new_task

Use below syntax to add logic:

namespace :test do
  desc 'Test new task'
  task new_task: :environment do
    puts Parent.all.inspect
  end
end

Run above task using below command:

bundle exec rake test:new_task

or

 rake test:new_task
Ni3
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3

The :environment dependency is quite correctly called out, but rake still may not know about other gems that your models depend on - in one case of mine, 'protected_attributes'.

The answer is to run:

bundle exec rake test:new_task

This guarantees that the environment includes any gems specified in your Gemfile.

Lex Lindsey
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