问题
Big Update:
As I finally found the real solution, I also discovered the real problem. As I wrote down here a lot of useless information, considering the real problem, I'm making a huge update of the question so that other people can find easily what's going on and can see the solution.
The Problem: It's because of the assets pipeline of Rails 3.1
Actually... It's an easy one: the assets were rendered twice in development-environment. Doing lot of investigations shew me that my Rails 3.1 server was rendering the assets from both the "app/assets" and "public/assets" folders. So, I had every .js and .css files duplicated, which was breaking all my javascript animations (yeah... binding twice the same event and handler to the same element is not what you want... normally).
And if the problem appeared all of a sudden, that was because I had to run "rake assets:precompile" to deploy my application. Since that, when my application was running in development, the server was rendering the static precompiled assets and the dynamic precompiled assets.
The solution (there's now a better one few lines below) - but you can still read it
First one: I just had to delete all the precompiled assets from my public folder.
Better one: Add config.serve_static_assets = false to development.rb which will prevent loading files from /public/assets. Also, don't forget to reset your browser cache.
[Edit: July 20th 2012]
Advanced one: I recently had a new problem because of those static assets. You know, when you use paperclip or some other gem and they add your images in your public folder in some system sub-folder because it's better if you want to deploy your application using capistrano. Well, that's great but! As we added config.serve_static_assets=false, those images aren't rendered in development and that's bad if you want to do some css on them. So! What to do then?
Well in fact you'll have to turn on static assets in development like so:
# Expands the lines which load the assets
config.assets.debug = true
config.serve_static_assets = true
Then to prevent rails from rendering your other assets twice (the precompiled ones), just do this command:
rake assets:clean
It's the opposite of rake assets:precompile and will clean your public/assets folder so that Rails won't render your assets twice. Of course you'll still have to clean your browser cache and clean your assets each time you precompiled them.
[Edit: November 18th 2013] - From @idejuan answer
Another solution:
You can add this line:
config.assets.prefix = '/dev/assets'
To development.rb, where the prefix can be whatever you want. Scripts will not load twice anymore, and images in /public/system will be read! But be carefull as it changes the path to your "static" assets... if you require assets from a gem, it might not load them properly in development...
[End edit]
The remaining question with answer!
Well, why my development application was rendering static precompiled assets?
In fact if you precompile your assets localy, rails render assets from the public folder AND from the assets folder in development and test environment by default. Normally assets from the public folder should overwrite those from the assets folder, but it's not the case and even if it does, we would lost the benefits of the "debug_mode" as we would have to precompile assets each time. So... Assets are rendered twice when precompiled locally in development and test environment.
So, by adding "config.serve_static_assets = false" to your development.rb file, you somehow overwrite the default line that telling Rails to look in your public folder for assets. I hope they'll do something cleaner one day about locally precompiled assets.
Thanks to the ones who helped me for my investigations :).
Kulgar.
回答1:
You might want to look at
https://stackoverflow.com/a/7854902/686460
"Adding config.serve_static_assets = false to development.rb will prevent loading files from /public/assets"
I think that is a better solution than what you are suggesting here.
回答2:
I had the same problem and found an easy solution/hack to it. I just added this line:
config.assets.prefix = '/dev/assets'
to development.rb, where the prefix can be whatever you want, I put /dev/assets to avoid further confusion.
Scripts do not load twice anymore, and I can use the images I have in /public/system that could not be read when I tried the solution of config.serve_static_assets = false
So far I have not found disadvantages to this solution. Hope it serves to you as well!
回答3:
I can't see why an Ubuntu upgrade would have anything to do with your JavaScript. Are you using static JavaScript? Dynamic JavaScript? CoffeeScript? If one of the latter two, I suppose it's possible that the upgrade broke one of the tools that's processing your JS...
Some things to try:
- View the JavaScript source in your browser. Make sure that the same source code is reaching your browser.
- Try running the Rails app on a different system (perhaps install a second VM with a different Ubuntu version and see if you can replicate the problem).
- Make triple-sure that the exact same version of the app code is in both places.
回答4:
I would also suggest that you run the rails server passing it a different environment. This could be related to the Environment settings you have set up for development.
rails server -e production
If the problem disappears it has got to do with your config settings for the "development environment.
来源：https://stackoverflow.com/questions/8170039/ruby-on-rails-3-1-assets-pipeline-assets-rendered-twice