Issue using FBRequestConnection error handler for fetching Facebook data

As a developer, we often encounter issues when dealing with complex networking tasks. In this article, we’ll delve into the world of Facebook’s API and explore an issue related to using FBRequestConnection’s error handler for fetching Facebook data.

The Problem

The problem lies in the fact that FBRequestConnection is a callback-based system, which means that the code inside its completion block will be executed only when the request is completed. In this specific case, we’re trying to fetch all the friends’ details at once using FQL (Facebook Query Language) and store them in an array.

However, there’s a catch - the FBRequestConnection error handler is also a callback function that’s called when an error occurs during the request. This can lead to some unexpected behavior if not handled properly.

In this article, we’ll examine the code snippet provided by the OP (original poster) and identify the issue at hand.

The Code

Let’s take a closer look at the fetchFriendDetails method:

- (void)fetchFriendDetails {
    NSString* query = [NSString stringWithFormat:@"SELECT uid,name,birthday_date,pic_square FROM user WHERE uid IN (SELECT uid2 FROM friend WHERE uid1 = me())"];

    // Set up the query parameter
    NSDictionary *queryParam = [NSDictionary dictionaryWithObjectsAndKeys:
                                query, @"q", nil];

    // Make the API request that uses FQL
    [FBRequestConnection startWithGraphPath:@"/fql"
                                 parameters:queryParam
                                 HTTPMethod:@"GET"
                          completionHandler:^(FBRequestConnection *connection,
                                              id result,
                                              NSError *error) {
                              if (!error)
                              {
                                  NSArray *tempArray = [result valueForKey:@"data"]; 
                                  NSMutableArray *tempArrayAbout = [NSMutableArray arrayWithArray:tempArray]; 
                                  self.friendsDetailsArray = tempArrayAbout;
                                  NSLog(@"details are %@",friendsDetailsArray);
                              }
                          }];
}

The Issue

The issue arises when the syncSettings method is called, which triggers the fetchFriendDetails method. However, since FBRequestConnection’s error handler is a callback function, it doesn’t execute immediately.

As a result, the code inside the completion block (tempArrayAbout = [NSMutableArray arrayWithArray:tempArray]; self.friendsDetailsArray = tempArrayAbout;) is not executed until after the request has completed successfully. This can lead to unexpected behavior if there’s an error during the request.

The Solution

To resolve this issue, we need to ensure that the code inside the completion block is executed only after the request has completed successfully. We also need to handle any errors that may occur during the request.

Here are the key changes made to the original code:

- (void)fetchFriendDetails {
    NSString* query = [NSString stringWithFormat:@"SELECT uid,name,birthday_date,pic_square FROM user WHERE uid IN (SELECT uid2 FROM friend WHERE uid1 = me())"];

    // Set up the query parameter
    NSDictionary *queryParam = [NSDictionary dictionaryWithObjectsAndKeys:
                                query, @"q", nil];

    // Make the API request that uses FQL
    [FBRequestConnection startWithGraphPath:@"/fql"
                                 parameters:queryParam
                                 HTTPMethod:@"GET"
                          completionHandler:^(FBRequestConnection *connection,
                                              id result,
                                              NSError *error) {
                              if (error) {
                                  NSLog(@"Error occurred during the request: %@", error);
                              } else {
                                  // Fetch friends' details here
                                  NSArray *tempArray = [result valueForKey:@"data"]; 
                                  NSMutableArray *tempArrayAbout = [NSMutableArray arrayWithArray:tempArray]; 

                                  // Save friends' details to array
                                  self.friendsDetailsArray = tempArrayAbout;
                                  NSLog(@"Details are %@",friendsDetailsArray);
                              }
                          }];
}

Conclusion

In this article, we’ve explored the issue related to using FBRequestConnection’s error handler for fetching Facebook data. We’ve identified the problem and proposed a solution that ensures code execution only after successful request completion.

By handling errors properly and executing code inside the completion block in a controlled manner, we can avoid unexpected behavior and ensure a smooth development experience.

Note: This article assumes you have a basic understanding of Facebook’s API, FQL, and FBRequestConnection. If you’re new to this topic, I recommend checking out the official documentation and tutorials provided by Facebook.

Last modified on 2024-01-19