title: Facebook IOS SDK : how to do silent sign in?
body: <p>I have an app doing a facebook login, which works well, but everytime I reopen it I have to connect again to facebook to do the sign-in. I'm also using google sign-in sdk where I can call the function <code>gSignIn.signInSilently()</code>, is there something similar for facebook? I found <a href="https://developers.facebook.com/docs/facebook-login/reauthentication" rel="nofollow">this</a> for the javascript sdk but I don't know if it's possible for the ios SDK and how to use it in swift...</p>