How to handle optional Realm sync? - swift

Question

I have an app with local/offline Realm files/databases. I would like to add the option to log in to sync data across devices, and I figured Realm Object Server would be great for this. I know that when a user logs in, I will need to write a migration from a local realm to a synced realm. What do I do if a user decides to logout? What do I do if a user never logs in in the first place? Do I need to have two paths in my code (everywhere) to choose whether it should use the local or synced realm?

Answer 1

I use a RealmProvider class to get the realm instance.
class RealmProvider {
class func realm() -> Realm {
if let _ = NSClassFromString("XCTest") {
return try! Realm(configuration: Realm.Configuration(fileURL: nil, inMemoryIdentifier: "test", syncConfiguration: nil, encryptionKey: nil, readOnly: false, schemaVersion: 0, migrationBlock: nil, deleteRealmIfMigrationNeeded: true, objectTypes: nil))
} else {
let user = getUser()
guard let loggedInUser = user else {
do {
return try Realm()
} catch {
print(error)
}
return try! Realm()
}
// open up synced url to the username.
if let user = SyncUser.current {
let syncServerURL = URL(string: "realm://realm.myapp.com/~/\(loggedInUser.username.md5())")!
let config = Realm.Configuration(syncConfiguration: SyncConfiguration(user: user, realmURL: syncServerURL))
// Open the remote Realm
return try! Realm(configuration: config)
} else {
// login first.
let serverURL = URL(string: "http://realm.myapp.com")!
let token = getToken()
let customCredentials = SyncCredentials(customToken: token, provider: Provider("custom/myAuth"))
//
SyncUser.logIn(with: customCredentials,
server: serverURL) { user, _ in
if let user = user {
// can now open a synchronized Realm with this user
// Open Realm
let configuration = Realm.Configuration(
syncConfiguration: SyncConfiguration(user: user, realmURL: URL(string: "realm://realm.myapp.com/~/\(loggedInUser.username.md5())")!)
)
_ = try! Realm(configuration: configuration)
}
}
}
return try! Realm()
}
}
}
To answer your question,
What do I do if a user decides to logout?
The RealmProvider will give you a local realm file.
What do I do if a user never logs in in the first place?
The data will still be stored in a local realm file, once the user logs in, you can open up a synced realm and run the migration.
PS: There is one catch, if the synced realm is being opened the first time, it will still return the local realm file. :/