How renew Spotify session

[baillyjamy]

Hi,
I am implementing your library in my app and I have a little problem.
When my application is launched I'll want to restore my stored session then check if it's valid and renew it if necessary. I want also renew my access_token when i launch my application in a new device but I want to avoid interaction by the user. Then i would like store the refresh_token in my online DB.
But i can't access to the refresh token and I can't find a function to refresh my access_token with a refresh_token.
Do you have an idea of how to do it with your library ?
Thanks

[baillyjamy]

Finnally i use https://github.com/spotify/ios-sdk