Rails 3.1 and Image Assets

156
votes

I have put all my images for my admin theme in the assets folder within a folder called admin. Then I link to it like normal ie.

# Ruby    
image_tag "admin/file.jpg" .....
#CSS
.logo{ background:url('/assets/images/admin/logo.png');

FYI. Just for testing I am not using the asset_path tag just yet as I have not compiled my assets.

Ok all good so far until I decided to update an image. I replaced some colors but on reload the new styled image is not showing. If I view the image directly in the browser its still showing the old image. Going one step further I destroyed the admin images folder. But it has broken nothing all the images are still being displayed. And yes I have cleared my cache and have tried on multiple browsers.

Is there some sort of image caching going on? This is just local development using pow to serve the pages.

Even destroying the whole images folder the images are still being served.

Am I missing something?

7
ruby-on-railsruby-on-rails-3
that's not the case with 3.1 using the asset pipeline. You would use the command rake assets:precompile which will compress those files and move them to the public file – Lee
Well moving them to the public folder worked, all a bit strange as they worked fine being served from the assets folder. Maybe have to wait for more docs on 3.1. – Lee
I understand your frustration. Apparently release candidates don't get documented very well. – tybro0103
Leave them in assets, just don't include a folder path at all. See my answer below. – Andrew

7 Answers

226
votes

In 3.1 you just get rid of the 'images' part of the path. So an image that lives in /assets/images/example.png will actually be accessible in a get request at this url - /assets/example.png

Because the assets/images folder gets generated along with a new 3.1 app, this is the convention that they probably want you to follow. I think that's where image_tag will look for it, but I haven't tested that yet.

Also, during the RailsConf keynote, I remember D2h saying the the public folder should not have much in it anymore, mostly just error pages and a favicon.

98
votes

You'll want to change the extension of your css file from .css.scss to .css.scss.erb and do:

background-image:url(<%=asset_path "admin/logo.png"%>);

You may need to do a "hard refresh" to see changes. CMD+SHIFT+R on OSX browsers.

In production, make sure

rm -rf public/assets    
bundle exec rake assets:precompile RAILS_ENV=production

happens upon deployment.

22
votes

For what it's worth, when I did this I found that no folder should be include in the path in the css file. For instance if I have app/assets/images/example.png, and I put this in my css file...

div.example { background: url('example.png'); }

... then somehow it magically works. I figured this out by running the rake assets:precompile task, which just sucks everything out of all your load paths and dumps it in a junk drawer folder: public/assets. That's ironic, IMO...

In any case this means you don't need to put any folder paths, everything in your assets folders will all end up living in one huge directory. How this system resolves file name conflicts is unclear, you may need to be careful about that.

Kind of frustrating there aren't better docs out there for this big of a change.

16
votes

In rails 4 you can now use a css and sass helper image-url: 

div.logo {background-image: image-url("logo.png");}

If your background images aren't showing up consider looking at how you're referencing them in your stylesheets.

10
votes

when referencing images in CSS or in an IMG tag, use image-name.jpg

while the image is really located under ./assets/images/image-name.jpg

2
votes

http://railscasts.com/episodes/279-understanding-the-asset-pipeline

This railscast (Rails Tutorial video on asset pipeline) helps a lot to explain the paths in assets pipeline as well. I found it pretty useful, and actually watched it a few times.

The solution I chose is @Lee McAlilly's above, but this railscast helped me to understand why it works. Hope it helps!

0
votes

The asset pipeline in rails offers a method for this exact thing.

You simply add image_path('image filename') to your css or scss file and rails takes care of everything. For example:

.logo{ background:url(image_path('admin/logo.png'));

(note that it works just like in a .erb view, and you don't use "/assets" or "/assets/images" in the path)

Rails also offers other helper methods, and there's another answer here: How do I use reference images in Sass when using Rails 3.1?