Uninitialized constant AssetSync

Question

I used the gem asset_sync and aws to precompile my assets. rake assets:precompile works fine. After I pushed my app to heroku, and ``` heroku run rake db:migrate ``` I get the following error "uninitialized constant AssetSync" initializers/asset_sync.rb ``` AssetSync.configure do |config| config.fog_provider = 'AWS' config.aws_access_key_id = "..." config.aws_secret_access_key = "..." config.fog_directory = Rails.env + "-..." config.fog_region = 'eu-west-1' end ``` config/production.rb ``` config.action_controller.asset_host = "//#{ENV['FOG_DIRECTORY']}.s3.amazonaws.com" config.assets.enabled = true ``` After running run rake assets:precompile the first time, all my app/assets/images were moved to public/assets . I've deleted them from github and added public/assets/* to .gitignore. May this be the problem? Edit: when running git push heroku master, it looks like they were precompiled ``` Preparing app for Rails asset pipeline Running: rake assets:precompile AssetSync: using /tmp/buil…

Accepted Answer

Your initializer assumes that AssetSync is always defined, but this will not be the case if your `Gemfile` looks like:

```
group :assets do
  gem 'asset_sync'
end
```

The `asset_sync` documentation recommends wrapping the initializer in:

```
if defined?(AssetSync)
...
end
```

This is because Heroku runs `production` without the `assets` group of gems. Heroku precompiles your assets when you run a push -- and if `asset_sync` is enabled, it will update S3 at that time -- so when your application launches later, it no longer needs those gems. Thus, your `asset_sync` initializer needs to handle the situation where the gem is not loaded.

Uninitialized constant AssetSync

Solution

Problem