Facebook IOS SDK : how to do silent sign in? - ios

Question

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 gSignIn.signInSilently(), is there something similar for facebook? I found this for the javascript sdk but I don't know if it's possible for the ios SDK and how to use it in swift...

Answer 1

The Facebook SDK automatically maintains the login state, which can be confirmed by checking for the access token.
You can check for the access using the following method:
FBSDKAccessToken.currentAccessToken()
You can check for the presence of the token which would mean that the user is logged in.
Check the docs for more details.

Answer 2

i've tried this
if(![FBSDKAccessToken currentAccessToken])
{
FBSDKLoginManager *manager = [[FBSDKLoginManager alloc]init];
[manager logInWithReadPermissions:#[#"public_profile", #"email",#"user_photos"] handler:^(FBSDKLoginManagerLoginResult *result,NSError *error)
{
if(error == nil)
{
NSLog(#"Facebook - successfully login %#",result.token);
//login successfully
//do your stuff here
}
}];
}
else
{
//already login
//Do Your stuff here
}

Answer 3

I am saving the access token string and manually setting it on consecutive launches to bypass the re-login flow.
func loginWithFacebook() {
//Check for previous Access Token
if let accessToken = AccessToken.current {
//AccessToken was obtained during same session
getAccountDetails(withAccessToken: accessToken)
}
else if let strAuthenticationToken = UserDefaults.standard.string(forKey: "AccessToken_Facebook") {
//A previous access token string was saved so create the required AccessToken object
let accessToken = AccessToken(authenticationToken: strAuthenticationToken)
//Skip Login and directly proceed to get facebook profile data with an AccessToken
getAccountDetails(withAccessToken: accessToken)
}
else {
//Access Token was not available so do the normal login flow to obtain the Access Token
LoginManager().logIn(readPermissions: [.publicProfile, .email], viewController: nil) { loginResult in
switch loginResult {
case .failed(let error):
print(error)
case .cancelled:
print("User cancelled login.")
case .success(let grantedPermissions,
let declinedPermissions,
let accessToken):
//Save Access Token string for silent login purpose later
let strAuthenticationToken = accessToken.authenticationToken
UserDefaults.standard.set(strAuthenticationToken,
forKey: "AccessToken_Facebook")
//Proceed to get facebook profile data
self.getAccountDetails(withAccessToken: accessToken)
}
}
}
}
func getAccountDetails(withAccessToken accessToken: AccessToken) {
let graphRequest: GraphRequest = GraphRequest(graphPath : "me",
parameters : ["fields" : "id, name, email"],
accessToken : accessToken,
httpMethod : GraphRequestHTTPMethod.GET,
apiVersion : GraphAPIVersion.defaultVersion)
graphRequest.start { (response, result) in
switch result {
case .success(let resultResponse):
print(resultResponse)
case .failed(let error):
print(error)
}
}
}
NOTE: For the ease of this example, the Facebook Access Token string is being saved to UserDefaults but ideally it should be saved to the Keychain.
(Swift 4 / Facebook SDK 4.30)