Understanding the Facebook SDK 3.6 for iOS Error 2 on Device

As a developer, it’s not uncommon to encounter issues when integrating third-party libraries into our applications. The Facebook SDK 3.6 for iOS is no exception. In this article, we’ll delve into the world of Facebook authentication and explore the root cause of error 2 on device.

Background: Facebook Authentication with iOS

To authenticate users using the Facebook SDK, you need to create a Facebook session and open it with read permissions. The session state can be one of three states:

• FBSessionStateCreated: The user has logged in.
• FBSessionStateOpen: The user is currently logged in.
• FBSessionStateClosed: The user is no longer logged in.

To create a Facebook session, you need to create an instance of FBSession and initialize it. You can then open the session using the openActiveSessionWithReadPermissions:allowLoginUI: method.

The Problem: Error 2 on Device

When running the Facebook SDK on a real device (iPhone 4), the application crashes with error 2. The issue persists even when testing on an iOS simulator, which suggests that there might be a problem with the app’s architecture or configuration.

The Solution: Checking Session Login Sample

After digging through the Facebook documentation and various online forums, it appears that the solution lies in modifying the MyAppDelegate class. Specifically, you need to create a new session instance when the current one is not open or has been closed.

Here’s an excerpt from the modified code:

- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation {
    return [FBAppCall handleOpenURL:url sourceApplication:sourceApplication withSession:self.session];
}

- (void)applicationDidFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    if (!self.session.isOpen || self.session.state != FBSessionStateCreated) {
        // Create a new, logged out session.
        self.session = [[FBSession alloc] init];
    }
    
    // Open the active session with read permissions
    [self.session openWithCompletionHandler:^(FBSession *session,
                                             FBSessionState status, 
                                             NSError *error) {
        if (error != nil) {
            NSLog(@"Error creating session: %@", error);
        } else if (!session.isOpen) {
            NSLog(@"Session is not open");
        }
        
        [self sessionStateChanged:session state:status error:error];
    }];
}

Additional Explanation: Understanding FBAppCall

To understand the modified code, it’s essential to grasp how FBAppCall works. When a URL is opened by the app (e.g., when Facebook sends a link for login), Facebook creates an instance of FBAppCall. This object serves as a bridge between the app and Facebook’s authentication process.

By using FBAppCall, you can handle the incoming requests from Facebook and respond accordingly. In this case, we use it to open the active session with read permissions when the user clicks on the login link.

Best Practices: Managing Sessions

To avoid potential issues in your app’s architecture, consider implementing a best practice for managing sessions:

• Create a separate class or property to manage Facebook sessions.
• Use this class to initialize and close the session as needed.
• Update the app’s delegate methods (e.g., applicationDidFinishLaunchingWithOptions) when opening or closing the session.

Conclusion

By following these steps, you should be able to resolve error 2 on device using the Facebook SDK 3.6 for iOS. Always remember to:

• Check official documentation and forums for solutions.
• Be mindful of your app’s architecture and configuration.
• Implement best practices for managing sessions.

In conclusion, this article has provided a comprehensive guide to resolving Facebook SDK 3.6 for iOS error 2 on device. By understanding the underlying issues and implementing the suggested modifications, you’ll be well-equipped to handle authentication-related challenges in your next project.

Last modified on 2023-08-10