How do I integrate Facebook login on iOS?

Integrating Facebook login in an iOS app allows users to easily sign in using their Facebook credentials instead of creating a new account. This results in a much better user experience as it reduces friction during onboarding. It also helps apps access valuable profile data from Facebook that can be used for personalization and analytics.

Why should I integrate Facebook login in my iOS app?

Here are some of the key benefits of integrating Facebook login in your iOS app:

• Simplified signup and login for users. Users don’t need to remember another username and password.
• Access to profile data like name, profile photo, email, birthday, etc. This data can be used to prefill forms and personalize the experience.
• Ability to build social features using Facebook APIs and Facebook SDK.
• Higher conversion rates from new users who can sign up easily.
• Better analytics by getting structured user data from Facebook.

How does Facebook login work technically?

On a high level, these are the steps involved in implementing Facebook login in an iOS app:

1. User taps on “Login with Facebook” button.
2. The app makes a request to Facebook’s OAuth Dialog to get user’s permission.
3. If user approves, the Facebook SDK provides an access token to the app.
4. The app uses the access token to get profile and other data from Facebook API.
5. User is logged into the app using the Facebook profile data.

The access token allows the app to securely call Facebook APIs to get user data. The token expires after some time, so the app needs to handle refresh scenarios.

What do I need before integrating Facebook login?

Here are the prerequisites for adding Facebook login to an iOS app:

• An iOS app built in Swift or Objective-C using Xcode.
• An active Facebook App ID and App Secret. This can be obtained by creating an app on Facebook Developers page.
• The latest Facebook SDK for iOS added using CocoaPods or manually.
• Your app must be submitted for Facebook Login review before going live.

How do I install the Facebook SDK?

Here are the steps to install the Facebook SDK dependency in your iOS project:

1. Install CocoaPods if you don’t already have it:


$ sudo gem install cocoapods


2. Initialize CocoaPods in your project directory:


$ pod init


3. Open the Podfile and add the following line:


pod 'FBSDKLoginKit'


4. Install the dependency:


$ pod install


5. Open the .xcworkspace file to work with the CocoaPods dependencies.

The Facebook SDK is now installed and ready to be imported in your app!

How do I configure my app for Facebook Login?

After installing the Facebook SDK, follow these steps to configure your iOS app:

1. Log into the Facebook Developers dashboard and create a new app or select an existing one.
2. Add the bundle identifier of your iOS app under the Facebook Login product.
3. Make note of the App ID and App secret shown on the dashboard.
4. Open your Xcode project and select the application target.
5. Under Signing and Capabilities, enable Facebook Login.
6. Under Info tab, add your Facebook App ID under URL Types.
7. Import FBSDKLoginKit in your source files and provide the App ID.

Your app is now all set up with the required config to integrate Facebook Login!

How do I add the Login with Facebook button?

To allow users to login with Facebook, you need to add the Login with Facebook button in your app. Here is how to do it:

1. Add a UIButton to your view controller in Interface Builder.
2. Set the button Type to Custom.
3. Import FBSDKLoginKit in your file.
4. Set the button title as “Continue with Facebook”.
5. Set the button image to FBSDKLoginKit.facebookLoguinButtonIconImage.
6. Set the button background color to FBSDKLoginKit.facebookBlueColor.

Your Login with Facebook button is now ready! You can customize the text, font style as needed for your branding.

How do I implement the login flow?

When the user taps on the Login with Facebook button, we need to initiate the Facebook login flow. Here is how to do it:

1. Implement the loginButton() delegate method.
2. Create a LoginManager instance and call logIn() method.
3. Set the required read permissions to request from Facebook.
4. Handle the callback by checking the LoginResult object’s status.
5. If successful, get the access token and make Graph API calls.
6. On failure, show relevant error messages to user.

The Facebook SDK takes care of the OAuth dialog, token management and related flows. We just need to initiate login and handle the results.

How do I get user profile data?

Once you have a valid access token after user logs in, you can get profile information by making calls to the Facebook Graph API.

Here is how to fetch the user’s name, email and profile photo:

1. Create a GraphRequest for the “me” endpoint.
2. Set the “fields” parameter to declare required fields.
3. Make the API request using the active access token.
4. Parse the GraphResponse in the callback.
5. Extract the name, email and picture URL from the response.
6. Download the profile photo using the picture URL.

You can get various profile fields like birthday, location, feed etc. using the same GraphRequest technique.

How should I handle account linking?

When new users log in using Facebook, you need to handle account creation and linking it to the Facebook account. Here is one way to do it:

1. Check if a user already exists with the Facebook ID received.
2. If yes, link the login to the existing user account.
3. If no account exists, create a new user record in your database.
4. Save the Facebook ID, name, email and other data in the new user record.
5. Log the user into your app by creating a session tied to the user record.

This allows seamless login for returning users. New users have accounts automatically created based on their Facebook profile data.

How do I handle account switching?

It is common for Facebook users to be logged into multiple Facebook accounts on their device. Your app needs to handle switching between these accounts gracefully:

1. Detect account switching when your app comes foreground.
2. Logout the user from your app when this happens.
3. Clear any cached user data from previous account.
4. Show the Facebook login flow again to allow re-login.
5. Handle the new Facebook user as a fresh login in your app.

This ensures your users can easily switch between their Facebook accounts while using your app.

How do I log out a Facebook user?

To log out a user who logged in via Facebook, follow these steps:

1. Clear your app’s access token and any cached Facebook data.
2. Call the logOut() method of LoginManager.
3. Delete any user session data from your app.
4. Show your account login/signup screens again.

This will log the user fully out of both your app and Facebook. Logout callbacks can be used to update your app’s UI accordingly.

How should I handle errors and account deauthorization?

It is important to properly handle erros during Facebook login. The LoginResult object provides different error codes that you should handle:

• If login is cancelled, show a message asking user to login again.
• For other recoverable errors like network issue, retry login.
• For unrecoverable errors like invalid credentials, direct user to reset password.
• If account is deactivated, logout user fully and show appropriate message.

Proper error handling provides a smooth experience when things go wrong during Facebook login.

How do I submit my App for Login Review?

Before your app can go live with Facebook login, it needs to be submitted for Facebook Login Review. Here are the steps:

1. Go to Facebook Login section in your App Dashboard.
2. Click on “Start a Submission” and select your app.
3. Select type of app – Native or Hybrid.
4. For native app, upload the .ipa file of your iOS app.
5. Answer the compliance questions.
6. Submit for Review and wait for approval.

Once approved, your app will be live and available for all users to log in using their Facebook accounts.

Conclusion

Integrating Facebook login can significantly benefit your iOS app by providing a seamless sign-up flow. This results in more users willing to register and engage with your app. Handling the entire login flow properly right from SDK integration to error handling ensures your users have a smooth experience.