see tors/jquery-fileupload-rails#30

Author: Pietro Donatini

app/controllers/uploads_controller.rb

@@ -49,7 +49,7 @@ def create
           :content_type => 'text/html',
           :layout => false
         }
-        format.json { render json: [@upload.to_jq_upload].to_json, status: :created, location: @upload }
+        format.json { render json: {files: [@upload.to_jq_upload]}, status: :created, location: @upload }
       else
         format.html { render action: "new" }
         format.json { render json: @upload.errors, status: :unprocessable_entity }

app/views/uploads/index.html.erb

@@ -119,7 +119,7 @@
       // 
       // Load existing files:
       $.getJSON($('#fileupload').prop('action'), function (files) {
-        var fu = $('#fileupload').data('fileupload'), 
+        var fu = $('#fileupload').data('blueimpFileupload'), 
           template;
         fu._adjustMaxNumberOfFiles(-files.length);
         console.log(files);