Filling my model from Facebook data (<FBGraphUser>) - ios

Question

I created a model called User that have a property "name".
I'm making a request to facebook API (using the latest iOS SDK), the idea is set my user.name property when the facebook return the data.
The facebook return the data into the startWithCompletionHandler block, but I can't set this data to my user object, I only can access the data on startWithCompletionHandler. When I try access the data out of the block my model returns NULL.
How can I fill my model/object when facebook request returns?
My current method implementation:
+ (void)requestUserData:(User *)userModel {
if(FBSession.activeSession.isOpen) {
[[FBRequest requestForMe] startWithCompletionHandler:^(FBRequestConnection *connection, NSDictionary<FBGraphUser> *user, NSError *error) {
if(user.name) [self setUserData:user userModel:userModel];
}];
}
}
+ (void)setUserData:(NSDictionary<FBGraphUser> *)user userModel:(User *)userModel {
userModel.name = user.name;
}
And the call:
__block User *user = [[User alloc] init];
[GFFacebookHelpers requestUserData:user];
NSLog(#"user: %#", user.name); //this part prints 2013-06-06 18:03:43.731 FacebookClassTest[74172:c07] user: (null)
Thanks.

Answer 1

The Facebook's SDK is fetching asynchronously, so the completion handler you've written is executed after your helper method returns.
So when your method returns the User object of yours it is, logically just an empty user (since you alloc/init'ed it already).
When the completion block is invoked, that user object is updated but by this time, you're not processing it anymore in your app (view controller).
So here is my suggestion: Either use the Facebook SDK more directly from your view controllers, or if you want to keep all this logic in your helper class, then change it so your method doesn't return data, but it requires a block which will be invoked when the data request has finished, something more like this:
+ (void)requestUserDataWithCompletionHandler:(void (^)(User *user, NSError *error))handler{
if(FBSession.activeSession.isOpen) {
[[FBRequest requestForMe] startWithCompletionHandler:^(FBRequestConnection *connection, NSDictionary<FBGraphUser> *user, NSError *error) {
if(!error){
User *userData = [[User alloc] init];
userData.name = user.name;
dispatch_async(dispatch_get_main_queue(), ^{
handler(userData, nil);
});
}
else{
dispatch_async(dispatch_get_main_queue(), ^{
handler(nil, error);
});
}
}];
}
}
Note I've wrapped the invocation of the handler block in a dispatch_async() to the main queue to make sure you're good to go to update any UI.
Your view controller's method will now look like this:
- (void)updateStatusLabels {
if([GFFacebookHelpers isLogged]){
[GFFacebookHelpers requestUserDataWithCompletionHandler:^(User *user, NSError *error) {
if(!error){
self.fbStatus.text = user.name;
[_loginButton setTitle:#"Logout" forState:UIControlStateNormal];
}
}];
}else{
self.fbStatus.text = #"You need to login";
[_loginButton setTitle:#"Login" forState:UIControlStateNormal];
}
}