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florian thomas

Prevent 404s for missing uploads in your rails app

Every software developer has to deal with bugs in their apps and reproducing those. Some of these cases require a production database clone. In that case you’d probably just pull the most recent database backup from production and use it on your local machine. What is missing in those backups though, are the images uploaded by your users. This can be very annoying especially if you work on stuff like a media center which i did recently. To prevent those 404 errors from popping up in your browser’s developer console, while at the same time not needing to store gigabytes from user uploaded content in your locale filesystem, a rack middleware can help you.

As you can see in the gist above, we define a middleware called UploadsFallback and check in Line 8 if the current request is requesting a missing uploaded image. If that is the case we’ll return a fallback image to the client instead.

Lastly we need to tell Rails to load our UploadsFallback middleware. As we only want this to happen in development we add the following line to the /config/environments/development.rb file.

Restart your app and 404s for missing uploads are gone.