unknown wrote in post #1108500:
Currently i am using devise for authentication on my ruby on rails back end but I do not have any idea of how to link my rails app with an ios app. Are there any tutorials that show how to create a login in my iOS app?
It depends on what technique you want to use within your iOS app.
There are at least a couple of options:
1. Maintain login state via cookies (like a web browser).
NSURLConnection supports cookies, just like a web browser would. You login the same way as you would from a web browser. NSURLConnection will pass any associated cookies it received from the server back with each NSRequest.
It is also a good idea to store the user credentials in the iOS keychain. The keychain is based on the older C API so can be a bit tricky to work with, but there exists an Objective-C wrapper for the keychain in Apple's sample code. I modified their sample code somewhat to take advantage of modern Objective-C features such as ARC. I could make that available to you upon request.
2. Use stateless authentication (token based).
You can see examples of taken based authentication as used by sites such as GitHub. You would have users log into the web site and generate a user specific API token and enter that token into the iOS app. Once this is setup then it's just a matter of including the authentication token somewhere in your NSRequest. A good place to put that would be a custom request header (e.g. X-Auth-token). Then lookup and authenticate the user based on their generated token.
The advantage here is that there's no state to maintain within the iOS app. So if the iOS user were to clear their internet cache it would not force them to log in again.
Note: While it's trivial to make HTTP requests from an iOS app using NSURLConnection, it is a lot more complex to make networking robust. For instance NSURLConnection has a method for sending synchronous request that is very easy to use. However, you never want to use that on the main thread. Doing so puts your app at risk of either blocking UI updates, or in some cases cause the watchdog to kill your app. It is vital to perform all network operations on a background queue.
