Access Rails 4 Fingerprinted Image Asset from Javascript Variable Image Name

Question

Using Rails 4 on Heroku, precompiling assets and adding fingerprints.

I can access the assets from my erb files using:

<%= asset-url("image_name.jpg") %>

However, I'm making an ajax call to a controller to get a list of objects and I build an image name from each object, e.g. image-1.jpg, image-2.jpg, where the number here is from the javascript variable. These images are in the assets/images directory.

How can I link to them using the javascript variable, like this:

<%= asset-url("image-javascriptVariable.jpg") %>

This obviously doesn't work because it's rendered on the server well before the client renders the javascript variable.

Note: I know I could simply not preprocess/fingerprint these images and put them in public/assets and serve them static. However, I'd like to use the fingerprinting to break cache on updates.

Answer 1

You can't : erb/haml's interpolation run before rendering view (javascript here).

You should deport your logic in ruby in order to dynamically serve different assets files.

Answer 2

If the amount of images is reasonable you can use ERB to build a data structure in Javascript (p.e. dictionary) of all images and pick the right image name later.