I have a rails application currently running ,I want to make a mobile application for it ,I don\'t want to learn objective-c or java ,I read many articles about phonegap and how
You don't need to create a API. I had a similar situation, and used just Rails, Cordova/PhoneGap, Bootstrap, and a few Cordova plugins.
I ran into 2 main gothchas: how to get the correct assets loaded into the app's page, and how to tell an app access from a "browser" access on the same device.
My app required that I have a slightly different set of plugins for iOS and Android. So I needed a way to bundle up just the right set for each. I used multiple manifest files in the app/assets/javascripts directory to handle that.
I also modified the user-agent strings coming from my Cordova apps. By default, you can't really tell a "browser" GET from a Cordova app GET.