objective c How to refresh Access Token using Refresh Token - ios

Question

I am using Cognito user pool to authenticate users in my system. A successful authentication gives an ID Token (JWT), Access Token (JWT).Every one hour the  TokenExpiration . My question is once my Access Token expires, how do I use the stored refresh token to refresh my access token again?This is my code.
- (void)loginAWSMethod {
NSString *emailId = #"the email";
NSString *pwdTxt = #"the password";
NSLog(#"entered the login method %# %#",emailId,pwdTxt);
AWSCognitoIdentityUser *user = [pool getUser:emailId];
[[user getSession:emailId password:pwdTxt validationData:nil]
continueWithBlock:^id _Nullable(AWSTask<AWSCognitoIdentityUserSession *> * _Nonnull task)
{
if (task.error) {
dispatch_async(dispatch_get_main_queue(), ^{
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"ERROR CATCHED++++++");
UIAlertController * alert = [UIAlertController
alertControllerWithTitle:#"Incorrect email or password."
message:#""
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* yesButton = [UIAlertAction actionWithTitle:#"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action)
{
}];
[alert addAction:yesButton];
[self presentViewController:alert animated:YES completion:nil];
});
[self removeWaitingProgress];
});
}else{
NSLog(#"the result is %#",task.result);
AWSCognitoIdentityUserSession *response1 = task.result;
token = response1.accessToken.tokenString;
NSLog(#"the token is %#",token);
[[user getDetails] continueWithSuccessBlock:^id _Nullable(AWSTask<AWSCognitoIdentityUserGetDetailsResponse *> * _Nonnull task) {
AWSCognitoIdentityUserGetDetailsResponse *response = task.result;
for (AWSCognitoIdentityUserAttributeType *attribute in response.userAttributes) {
//print the user attributes
NSLog(#"Attribute: %# Value: %#", attribute.name, attribute.value);
if([attribute.name isEqualToString:#"sub"]){
cognitoID = attribute.value;
}
[defaults setValue:token forKey:#"token"];
[defaults setValue:#"yes" forKey:#"isLoggedIn"];
[defaults synchronize];
dispatch_async(dispatch_get_main_queue(), ^{
[self removeWaitingProgress];
[self gotoDashborad];
});
}
return nil;
}];
}
return nil;
}];
}

Answer 1

You should be able to simply invoke -[AWSCognitoIdentityUser getSession], which behind the scenes will either return the currently valid access token, or exchange the refresh token for new access token:
-(nullable NSString *)accessTokenStringForCurrentUser {
AWSCognitoIdentityUser *currentUser = [pool currentUser];
__block NSString *tokenString;
// `getSession` automatically exchanges the refresh token for a valid access token if needed
[[[currentUser getSession] continueWithBlock:^id _Nullable(AWSTask<AWSCognitoIdentityUserSession *> * _Nonnull task) {
// (Error handling not shown)
if (task.result) {
AWSCognitoIdentityUserSessionToken *accessToken = task.result.accessToken;
tokenString = accessToken.tokenString;
}
return nil;
}] waitUntilFinished];
return tokenString;
}
You may also wish to look at the Cognito UserPools Sample app which has Objective C samples of using UserPools.