Realm Swift why the migration block never been called

MongoDB Atlas App Services & Realm Realm
1

My code is like this

class RealmDatabaseManager{
    var realm:Realm!
    let container = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: ProjectSettings.group)!
    static let shared = RealmDatabaseManager()
    init(){
        let defaultURL = Realm.Configuration.defaultConfiguration.fileURL
        let realmURL = container.appendingPathComponent("default.realm")
        //check if there's file in realmurl
        let fileManager = FileManager.default

        if !fileManager.fileExists(atPath: realmURL.path) {
            try? fileManager.copyItem(at: defaultURL!, to: realmURL)
        }
        // Config init
        let config = Realm.Configuration(fileURL: realmURL, schemaVersion: 9,migrationBlock: {migration,oldVersion in
            if oldVersion < 3 {
               migration.enumerateObjects(ofType: WordRecordRealm.className()) { oldObject, newObject in
                   if let asset = oldObject!["noteCards"] as? RealmSwift.List<WordNoteRealm>{
                       newObject!["lookUpTime"] = asset.first?.decodedObject.addTime ?? Date.now.timeIntervalSince1970
                   }
                   else{
                       newObject!["lookUpTime"] = Date.now.timeIntervalSince1970
                   }
               }
                if oldVersion < 9{
                    migration.enumerateObjects(ofType: WordRecordRealm.className()) { oldObject, newObject in
                        let t = oldObject!["translations"]!
                        print(t)
                        newObject!["originalTranslations"] = t
                    }
                }
           }
        })
        Realm.Configuration.defaultConfiguration = config
        realm = try! Realm(configuration: config)
    }
}
3

There are a few things that would cause it to fail but more information is needed.

Did you verify the file located at

Realm.Configuration(fileURL: realmURL

realmURL is a valid file and needs to be migrated?

When you say the migration block is never called - what isn’t called? e.g. if you add a breakpoint to your code here

let config = Realm.Configuration(

run the code and step through it line by line, at what point does it fail? And when it does, what specific thing is failing?

4

After some trying, this is what I found. Do you have any idea about that?

5

Found the solution, It turns out that my widget always init the shared object ahead of the main app environment being loaded. then I create a class

class RealmConfiguration{
    static let realmURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: ProjectSettings.group)!.appendingPathComponent("default.realm")
    static func getConfig()->Realm.Configuration{
        let config = Realm.Configuration(fileURL: RealmConfiguration.realmURL,schemaVersion: 40) { migration, oldVersion in
            if oldVersion < 3 {
               migration.enumerateObjects(ofType: WordRecordRealm.className()) { oldObject, newObject in
                  
        }
        return config
    }
}

I call this function in the main app’s environment, and instead of init the widget using the shared realm object, I use @ObservedResults and set the realm default config to this config in the timeline provider’s init function. Now everything seems to work fine.