Using universal links

# Using universal links

You can improve the security of your app with Apple's universal links (opens new window) feature that securely communicates information between apps. If you set up a universal link, LINE tries to open your app with the universal link first. If the universal link is invalid, LINE falls back to a URL based on your iOS bundle ID (see Linking your app to your channel).

Universal links are recommended

Although universal links are optional, we recommend using them to make your app more secure.

To enable users to open your app with a universal link, follow these steps:

Create an association between your app and your server.
Set up a universal link on the LINE Developers Console.
Call the LoginManager.setup method with the universal link.
Handle the login result after your app is opened by the universal link.

# 1. Create an association between your app and your server

For this step, see Allowing Apps and Websites to Link to Your Content (opens new window) by Apple.

Complete these tasks:

Create an apple-app-site-association file that contains JSON data about the URLs that your app can handle and put it in your HTTPS server.
Add an Associated Domains entitlement to your app.

This section assumes that you use https://yourdomain.com/line-auth/ as the universal link to handle a LINE authorization response.

Include /line-auth/* in the paths field of your apple-app-site-association file. An example of a valid Apple App Site Association file looks like below:

{
    "applinks": {
        "apps": [],
        "details": [
            {
                "appID": "YOUR_TEAM_ID.com.yourcompany.yourapp",
                "paths": [ "/line-auth/*" ]
            }
        ]
    }
}

Note that you can test universal links only on a real iOS device. You need to set up your app ID and profile correctly. If your universal links don’t work, see Troubleshooting Universal Links (opens new window) on Apple's developer site. Ensure that your universal links work before you proceed with the next steps.

# 2. Set up a universal link on the LINE Developers Console

For the procedure, see Linking your app to your channel. In this example, we set it to https://yourdomain.com/line-auth/.

# 3. Call the `LoginManager.setup` method with the universal link

Pass the universal link to the LINE SDK for iOS Swift when you call the LoginManager.setup method. This lets LINE Login verify that the link is correctly set up on both the LINE Developers Console and your app to prevent the universal link from being abused. In the example below, the universal link is https://yourdomain.com/line-auth/.

let link = URL(string: "https://yourdomain.com/line-auth/")
LoginManager.shared.setup(channelID: "YOUR_CHANNEL_ID", universalLinkURL: link)

For more information about calling the LoginManager.setup method, see Integrating LINE Login with your iOS app.

# 4. Handle the login result after your app is opened by the universal link

To handle the authentication result returned from the LINE Platform, pass the received URL to the application(_:open:options:) method of LoginManager. This means modifying either your app delegate class or your scene delegate classes, depending on whether your project supports multiple windows (a feature introduced in iOS 13 (opens new window)).

# Modify app delegate

iOS 12 and earlier will open URLs by calling your UIApplicationDelegate object. If your app delegate class contains an application(_:continue:restorationHandler:) delegate method, add the following lines to it. If it doesn't exist, create it first, then add these lines:

func application(
    _ app: UIApplication,
    continue userActivity: NSUserActivity,
    restorationHandler: @escaping ([UIUserActivityRestoring]?) -> Void) -> Bool
{
    if LoginManager.shared.application(app, open: userActivity.webpageURL) {
        return true
    }
    // Your other code to handle universal links and/or user activities.
}

# Modify scene delegates

By default, iOS 13 or later will try to open URLs by calling a UISceneDelegate object.

If you created your project with Xcode 11 or later, then by default it will contain a SceneDelegate.swift file and your Info.plist file will contain a UIApplicationSceneManifest entry.

If your app supports multiple windows, add the following lines to any scene delegate class you want to use:

// SceneDelegate.swift
func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>) {
    _ = LoginManager.shared.application(.shared, open: URLContexts.first?.url)
}