How to get a new access token after expiration using OAuth 2.0 along with Youtube API in iOS application

Question

I am using the Youtube Api in my iPad application. i managed to get authenticated and get the access token using the OAuth 2.0. my problem is that the token expires after one hour and i don't know how to get a new one using the refresh-token without going through the authentication process again. i am using XCode 4.5 and iOS 5.1 & 6

Answer 1

According do the documentation

If your application obtains a refresh token during the authorization process, then you will need to periodically use that token to obtain a new, valid access token. Server-side web applications, installed applications, and devices all obtain refresh tokens.

So if you already have your refresh token, you just need to perform a POST request configured as follows

POST /o/oauth2/token HTTP/1.1
Host: accounts.google.com
Content-Type: application/x-www-form-urlencoded

client_id=21302922996.apps.googleusercontent.com&
client_secret=<YOUR CLIENT SECRET>
refresh_token=<YOUR REFRESH TOKEN>
grant_type=refresh_token

and you'll get back a response like

{
  "access_token":<A NEW ACCESS TOKEN>,
  "expires_in":<AN EXPIRING TIME>,
  "token_type":"Bearer"
}