Adding the Notification Plugin

Add the BreezSDKLiquid cocoapod to your iOS Podfile, with the target NotificationService. You can add any other dependencies your require here also, for example KeychainAccess to read the saved mnemonic from the keychain.

target 'NotificationService' do
  pod 'BreezSDKLiquid'
  pod 'KeychainAccess'
end

Once added to the Podfile, run pod install to install the dependencies.

More installation methods, including with the Swift Package Manager, can be found in the breez-sdk-liquid-swift repository.

Integrate the Notification Plugin

You're ready to add some Swift code to implement the Notification Plugin in your NotificationService target. In Xcode, in the NotificationService folder, open the Swift file named NotificationService.swift.

This Swift file should implement the Notification Plugin's SDKNotificationService class. The SDKNotificationService class handles the incoming notification content and processes the event. To properly implement this class, the NotificationService needs to override at least the getConnectRequest function. The getConnectRequest function is called by the SDKNotificationService to get a ConnectRequest which contains the data necessary to connect to the SDK. This data includes the Breez API key, the Config with its workingDir and the mnemonic.

Developer note

When using the Notification Plugin on iOS, it is important to note that the Config workingDir needs to be set to the app group's shared directory in both the NotificationService target and in the main application target, whether that is a Swift, Flutter or React Native based application.

Developer note

When accessing the Keychain using the Keychain Group, the AppIdentifierPrefix needs to be prepended to the configured identifier, like <TEAM_ID>.com.example.SharedKeychain. This Keychain Group needs to be used in the main application target as the accessGroup when you want to store anything on the keychain that later needs to be accessed by the notification service. 
import UserNotifications
import KeychainAccess
import BreezSDKLiquid

fileprivate let logger = OSLog(
    subsystem: Bundle.main.bundleIdentifier!,
    category: "NotificationService"
)

fileprivate let appGroup = "group.com.example.application"
fileprivate let keychainGroup = "A352BFE4OR.com.example.SharedKeychain"
fileprivate let accountMnemonic: String = "BREEZ_SDK_LIQUID_SEED_MNEMONIC"
fileprivate let accountApiKey: String = "BREEZ_SDK_API_KEY"

class NotificationService: SDKNotificationService {
    // Override the `getConnectRequest` function
    override func getConnectRequest() -> ConnectRequest? {
        // Get the Breez API key from the target bundle's Info.plist
        guard let apiKey = Bundle.main.object(forInfoDictionaryKey: accountApiKey) as? String else {
            os_log(.error, "API key not found")
            return nil
        }
        var config = defaultConfig(network: LiquidNetwork.mainnet, breezApiKey: apiKey)
        // Set the workingDir as the app group's shared directory,
        // this should be the same directory as the main application uses
        config.workingDir = FileManager
            .default.containerURL(forSecurityApplicationGroupIdentifier: appGroup)!
            .appendingPathComponent("breezSdkLiquid", isDirectory: true)
            .path

        // Get the mnemonic from the shared keychain using the same 
        // service name as the main application
        let service = Bundle.main.bundleIdentifier!.replacingOccurrences(of: ".NotificationService", with: "")
        let keychain = Keychain(service: service, accessGroup: keychainGroup)
        guard let mnemonic = try? keychain.getString(accountMnemonic) else {
            os_log(.error, "Mnemonic not found")
            return nil
        }
        return ConnectRequest(config: config, mnemonic: mnemonic)
    }
}

Reference implementation

For a complete reference, see how we implemented it in misty-breez wallet: NotificationService.swift.