Good example for a json webservice in Ruby on Rails

I want to create a Webservice Client first time via Ruby on Rails which sends json to an API. The json will contain a byte array. On my index I want to load the objects from the API. I want to use dropzone.js, too. If I search this I get a lot of examples how to create the API but I just want to build the service which shows and posts. Have you some ideas or really nice examples for me?