How to access current firebase user from iOS App Extension.

code.swift

import Foundation
import KeychainAccess //https://github.com/kishikawakatsumi/KeychainAccess
import Firebase 

//Requires shared Keychain with the same group name

class ApplicationBuilder {

    enum Target {
        case app
        case appExtension
    }

    private static let appKeychain = Keychain(service: "firebase_auth_{hosted app firebase application id}") //need replace　with　GOOGLE_APP_ID from GoogleService-Info.plist
    private static let extensionKeychain = Keychain(service: "firebase_auth_{app extension firebase application id}") //need replace　with　GOOGLE_APP_ID from GoogleService-Info.plist
    private static let userKeychainKey = "firebase_auth_1___FIRAPP_DEFAULT_firebase_user" //__FIRAPP_DEFAULT is FirebaseApp.name

    private static var target: Target = .app

    static func setup(target: Target, completion: @escaping () -> Void) {
        ApplicationBuilder.target = target

        if FirebaseApp.app() == nil {
            FirebaseApp.configure()
        }

        if target == .appExtension {
            syncFirebaseKeychain()
        }
    }

    private static func syncFirebaseKeychain() {
        guard let data = (try? appKeychain.getData(userKeychainKey)) as? Data else {
            try! extensionKeychain.remove(userKeychainKey)
            return
        }

        try? extensionKeychain.set(data, key: userKeychainKey)
    }
  
  //...

note.md

firebase-ios-sdk/FIRAuth.m at 1395c8202b236188b9e4e1bfc2a3e00244179593 · firebase/firebase-ios-sdk

firebase-ios-sdk/FIRAuth.m at 1395c8202b236188b9e4e1bfc2a3e00244179593 · firebase/firebase-ios-sdk

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