Facebook loginViewFetchedUserInfo is called twice - iphone

Question

I am using facebook SDK 3.0 in my app. The delegate method is called twice when after logging to facebook.
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView
user:(id<FBGraphUser>)user {
//loginThroughFb=TRUE;
NSString *userId=[[NSString alloc] initWithString:[user id]];
[self soapCallForLogin:#"" password:#"" deviceId:#"" fbid:userId];
NSLog(#"%#",userId);
[userId release];
}

Answer 1

I tried 'HelloFacebookSample' project and the method is called only once.
So I guess the best solution for such case is to keep a reference to the last user object and compare it to the new object you get the next call, and if they're equal you can just ignore that call.
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user {
if (![self isUser:cachedUser equalToUser:user]) {
cachedUser = user;
/// Do something
}
}
- (BOOL)isUser:(id<FBGraphUser>)firstUser equalToUser:(id<FBGraphUser>)secondUser {
return
[firstUser.objectID isEqual:secondUser.objectID] &&
[firstUser.name isEqual:secondUser.name] &&
[firstUser.first_name isEqual:secondUser.first_name] &&
[firstUser.middle_name isEqual:secondUser.middle_name] &&
[firstUser.last_name isEqual:secondUser.last_name] &&
...
}

Answer 2

I also had this problem. I managed to fix it with an ugly hack, but it works. I keep a counter in the FBLoginView delegate. When the fetchedUserInfo is called, I check the counter. If it is greater than zero, return. Otherwise, do two things -
1. increment the message counter
2. Fire a delayed event that zeroes the message counter again.
So your fetchedUserInfo method will look like this:
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView
user:(id<FBGraphUser>)user {
if ([self messageCounter] >0)
return;
else
{
self.messageCounter++;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 3 * NSEC_PER_SEC), dispatch_get_current_queue(), ^{
[self setMessageCounter:0];
});}
// Do whatever you were going to do }

Answer 3

Fixed in FB SDK 3.8 released on Sept 18 2013. The delegate methods are now called once per login regardless of how many times the repeated logging out and back in occur.
I was also able to reproduce this on FB SDK 3.7.1 and within their own sample program "Scrumptious"
As mentioned (at least for me) this only happens after:
Logging in once
Logging out
Logging back in (Now it happens)
What is interesting is the order of calls on re-logins:
On the first login I the calls I see are:
- (void)loginViewShowingLoggedInUser:(FBLoginView *)loginView;
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user;
On the 2nd (and later) logins I see:
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user;
- (void)loginViewShowingLoggedInUser:(FBLoginView *)loginView;
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user;
Which gives a handy little workaround of setting a flag in the middle method like so:
- (void)loginViewShowingLoggedInUser:(FBLoginView *)loginView {
// Set flag
self.isFirstLoginDone = YES;
}
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user {
// Check
if(self.isFirstLoginDone) {
// Execute code I want to run just once
NSLog(#"fetched");
}
// Don't forget to clear the flag (I guess it shouldn't matter if everything is cleaned up)
self.isFirstLoginDone = NO;
}

Answer 4

There could be another reason, which i jsut faced.
My situation:
ViewController A has a login (With fbloginview and its delegate set)
User chooses to register, moves to ViewController B with another fbloginview and its delegate set.
The above makes the delegate fire twice.
I have fixed this by setting delegate to nil on ViewWillDisappear in ViewController A.
-(void) viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
fbLoginButton.delegate=self;
}
-(void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
fbLoginButton.delegate=nil;
}

Answer 5

I used this simple trick :
(Define an int facebookCounter in your interface)
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView
user:(id<FBGraphUser>)user {
if (self.facebookCounter==0) {
self.facebookCounter++;
return;
}
//Do stuff here
}

Answer 6

I needed to add thread safety in this method. A simple class variable did not work. The following two options will work, depending on the use case-
- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView user:(id<FBGraphUser>)user {
//self.executedOnce = NO; in the init method of this class
#synchronized(self){
if(!self.executedOnce) {
//do something once per init of this class
self.executedOnce = YES;
}
}
//OR- This will only execute once in the lifetime of the app, thus no need for the executedOnce flag
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
//do something once per lifetime of the app
});
}

Answer 7

just in the loginViewFetchedUserInfo method set the delegate of the loginView to nil. then it can never be called. and if you need the login again, set the delegate to the correct object.