保存Facebook好友-iOS

Question

I'm new to iOS development and I'm trying to integrate my app with Facebook. I'm already passed the step of the login and now I'm trying to get the user friends list.

I need to have the users IDs in a list seperated by ';' so I have the following code in place:

-(NSMutableString *) getUserFacebookFriendsList
{    
    NSMutableString *userFBFriends = [[NSMutableString alloc] init];

    [FBRequestConnection startWithGraphPath:@"/me/friends" 
                                 parameters:nil 
                                 HTTPMethod:@"GET"
                          completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
        for (NSDictionary *friendData in [result objectForKey:@"data"])
        {
            NSMutableString  *friendId = [friendData objectForKey:@"id"];
            [userFBFriends appendString:friendId];
            [userFBFriends appendString:@";"];
            NSString *FBFriendsList = [NSString stringWithFormat:userFBFriends];
        }
    }];

    return userFBFriends;
}

Now when I debug the call I can see that I do get the user's friends but the problem is when I get to the return statemtn, it seems like my variable "userFBFriends" is empty....

Any idea what I am missing here ?

---

Following the answer that I got I would like to post the following code that I have now and maybe someone can help me with the problem.

- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView
                            user:(id<FBGraphUser>)user {
    NSLog(@"test login facebook");
    NSLog(@"the facbook user borthday is : %@",[user birthday]);
    NSLog(@"The FACEBOOK user ID is : %@", [user objectID]);
    NSLog( @"### running FB sdk version: %@", [FBSettings sdkVersion] );
   // FBRequestConnection* conn = [[FBRequestConnection alloc] init];


    NSLog(@"User's friends list as will be sent to the server is : %@", **XXXXXXX** );

}


-(void) getUserFacebookFriendsList {
    NSMutableString *userFBFriends = [[NSMutableString alloc] init];


    [FBRequestConnection startWithGraphPath:@"/me/friends" parameters:nil HTTPMethod:@"GET" completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
        for (NSDictionary *friendData in [result objectForKey:@"data"])
        {
            NSMutableString  *friendId = [friendData objectForKey:@"id"];
            [userFBFriends appendString:friendId];
            [userFBFriends appendString:@";"];

            // This will call -didLoadFacebookFriends on the main thread.
            __weak __typeof(self) weakSelf = self;
            dispatch_async(dispatch_get_main_queue(), ^{
                [weakSelf didLoadFacebookFriends:userFBFriends];
                });
        }
    }];
}

-(void) didLoadFacebookFriends:(NSMutableString *)facebookFriends {
    // Do your stuff here.
    NSLog(@"The list of friends is : %@",facebookFriends);
}

Now my question is how can I get the friends list to be printed in the main function that actually do the call to the getUserFacebookFriendsList ? Because again it seems like the NSLOG call that I'm doing in the function "loginViewFetchedUserInfo" is running before the friends list was even generated. If you see in my code above I marked it in BOLD.

Thanks in advance for helping !

Answer 1

You need to be aware that your code does not run in a single line. There are sections in your code ( FBRequestConnection ) that will run in parallel to your other code. This is called concurrency . You'll have to wait till FBRequestConnection finished.

Here's your updated code:

- (void)loginViewFetchedUserInfo:(FBLoginView *)loginView
                            user:(id<FBGraphUser>)user {
    NSLog(@"test login facebook");
    NSLog(@"the facbook user borthday is : %@",[user birthday]);
    NSLog(@"The FACEBOOK user ID is : %@", [user objectID]);
    NSLog( @"### running FB sdk version: %@", [FBSettings sdkVersion] );

    [self getUserFacebookFriendsList];         
}


-(void) getUserFacebookFriendsList {
    NSLog("%@", @"Requesting facebook friends");

    [FBRequestConnection startWithGraphPath:@"/me/friends" parameters:nil HTTPMethod:@"GET" completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
        NSLog("%@", @"Request finished.");

        NSMutableString *userFBFriends = [[NSMutableString alloc] init];

        for (NSDictionary *friendData in [result objectForKey:@"data"]) {
            NSMutableString  *friendId = [friendData objectForKey:@"id"];
            [userFBFriends appendString:friendId];
            [userFBFriends appendString:@";"];
         }

         NSLog(@"%@", @"Finished parsing. Will call didLoadFacebookFriends:");
         __weak __typeof(self) weakSelf = self;
         dispatch_async(dispatch_get_main_queue(), ^{
             [weakSelf didLoadFacebookFriends:userFBFriends];
         });            
    }];
}

-(void) didLoadFacebookFriends:(NSString *)facebookFriends {
    NSLog(@"The list of friends is : %@",facebookFriends);

    // Do what you need to do.
}