Parse becomeInBackground is setting currentUser.sessionToken to null - ios

Question

I have an app that checks whether the current session is valid. So if you change the password on another phone, it will log you out of your other phones when you open the app. So, If there is a session token cached into [PFUser currentUser] I want to becomeInBackground with that token, and if it returns an error then that session is invalid and we should log out, else its valid and we have a new sessionToken. When I run this code I do not get any errors, and a user is returned with (null) for a .sessionToken
NSLog(#"Current Token: %#", [PFUser currentUser].sessionToken);
if ([PFUser currentUser].sessionToken) {
[PFUser becomeInBackground:[PFUser currentUser].sessionToken block:^(PFUser * _Nullable user, NSError * _Nullable error) {
if (error) {
NSLog(#"%#", error);
} else {
NSLog(#"Returned User Token: %#", user.sessionToken);
}
}];
}
this returns
Current Token: r:36ff500b036c041a37h9bab21f308741
Returned User Token: (null)
It's deleting the currentUser sessionToken! I have the most current Parse SDK (1.12.0) and I have no idea why it's doing this to me.

Answer 1

I believe this is happening as you are instructing the ParseSDK to become that other user, which looks like it doesn't work if it's the same as the current user (i.e. your session is valid).
I handle the session check a little bit differently. Instead, I refresh the user, then trap any errors and check for an invalid session. This works well :)
[[PFUser currentUser] fetchInBackgroundWithBlock:^(PFObject *object, NSError *error) {
if (error) {
NSLog(#"Error refreshing user %#", error.localizedDescription);
// check if the session token is invalid... force a logout!
if ([error.domain isEqualToString:PFParseErrorDomain] && error.code == kPFErrorInvalidSessionToken) {
dispatch_async(dispatch_get_main_queue(), ^{
[PFUser logOut];
// Show your login screen or whatever here
});
}
return;
}
}];