Question

I am experiencing some issues with the graph API on iOS.
I am trying to fetch all FB albums from an user. I noticed that by default, the graph API answer 25 first elements and then they provide next and/or previous urls to query the rest.

My problem is that I need to query every elements (not only the first 25) in one shot.

I tried using the limit parameter as explained in Facebook documentation, but I get an empty data array in response. When I remove the limit param, I can grab the 25 first elements.
Facebook API behaves in a similar way when I try with until=today or until=yesterday.

Here is the url I am using:
https://graph.facebook.com/me/albums?limit=0
0 is supposed to means no limit, I tried with 99999 same results.

I was wondering if someone already has that strange behavior from the Graph API?

Thank you for your help!

Answer 1

I finally found the problem.

There is a bug in the social network, it seams that Apple always append the string "?access_token=[ACCESS_TOKEN]" at the end of the url string.

According to that, if you put a parameter before in the URL string, the URL is not a valid as you’ll have two “?” in the string.

To avoid that I am using NSURLConnection class to manage the connection in this way:

NSString *appendChar = [[url absoluteString] rangeOfString:@"?"].location == NSNotFound ? @"?" : @"&";
NSString *finalURL = [[url absoluteString] stringByAppendingFormat:@"%@access_token=%@", appendChar, self.facebookAccount.credential.oauthToken];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:finalURL]];
NSURLResponse *response;
NSError *error;
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

if (error)
    [self.delegate facebookConnection:self didFailWithError:error];
else
{
    NSError *jsonError;
    NSDictionary *resultDictionnary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&jsonError];

    if (jsonError)
        [self.delegate facebookConnection:self didFailWithError:jsonError];
    else if ([resultDictionnary valueForKey:@"error"])
    {
        NSDictionary *errorDictionary = [resultDictionnary valueForKey:@"error"];
        NSError *facebookError = [NSError errorWithDomain:[errorDictionary valueForKey:@"message"] code:[[errorDictionary valueForKey:@"code"] integerValue] userInfo:nil];
        [self.delegate facebookConnection:self didFailWithError:facebookError];
    }
    else
        [self.delegate facebookConnection:self didFinishWithDictionary:resultDictionnary httpUrlResponse:response];
}

First I test the presence of the param character in the string and I append the correct one.
I give you as a bonus the way I handle the error.

I still use the social framework to get the credentials and connect the user:

    NSDictionary *accessParams = @{ACFacebookAppIdKey:kFacebookAppID, ACFacebookPermissionsKey:@[@"email", @"user_photos", @"user_activities", @"friends_photos"]};
ACAccountStore *accountStore = [[ACAccountStore alloc] init];
ACAccountType *accountType = [accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierFacebook];

[accountStore requestAccessToAccountsWithType:accountType options:accessParams completion:^(BOOL granted, NSError *error)
 {
     if (granted)
     {
         NSArray *facebookAccounts = [accountStore accountsWithAccountType:accountType];

         if ([facebookAccounts count] > 0)
         {
             self.facebookAccount = [facebookAccounts objectAtIndex:0];
             self.accessToken = self.facebookAccount.credential.oauthToken;
             [self.delegate facebookConnectionAccountHasBeenSettedUp:self];
         }
     }
     else
        [self.delegate facebookConnection:self didFailWithError:error];
 }];

In this code I don’t handle multiple facebook accounts but you can easily transform that snippet to handle it in your own way. Also, the connection is sent synchronously because I am using GCD to avoid blocking my interface but you can implement an asynchronous method built in the NSURLConnection class.

Hope this will help someone !