Dart Future wait to complete before calling another Future-CodePudding

Looking for help here guys. I have 2 Futures that populate data in sqflite. I need one (_insertInitialData()) to finish first before calling the second one (_insertAdditionalData()). I have done it this way, but it's not working. It first does the re-recreation of the DB as expected, then both _insertInitialData() and _insertAdditionalData() not in the order I expected. I have tried .whenComplete and calling here _insertAdditionalData() and also have tried different ways that I think should work but nothing.

This is just something I'm doing for fun but still I'd like to know what I'm doing wrong.

TIA

Future<void> _insertAdditionalData() async{}

void populateDB() {
  try {
   final localDB = LocalDatabase.instance;
   Future.wait([localDB.dropDB(recreateDB: true)]).then((_){
    print('DB recreated!');
    Future.wait([_insertInitialData()]).then((_) {
     print('_insertInitialData done');
     Future.wait([_insertAdditionalData()]).then((_){
      print('_insertAdditionalData done');
     });
    });

   });
  } catch (ex) {
   print('There was a problem in populateDB(): $ex');
  }
 }```

CodePudding user response：

Using await makes things a lot easier to read and will block execution of later lines until the action has finished.

Future<void> populateDB() async {
  final localDB = LocalDatabase.instance;
  await localDB.dropDB(recreateDB: true);
  print('DB recreated!');
  await _insertInitialData();
  print('_insertInitialData done');
  await _insertAdditionalData();
  print('_insertAdditionalData done');
}

CodePudding user response：

You can try using only one future statement, and follows it with multiple "then". This makes sure the first "then" will be completed before the second "then" is executed. I assume your localDB.dropDB(recreateDB: true) function is asynchronous.

Future<void> _insertAdditionalData() async{}

void populateDB() {
  try {
    final localDB = LocalDatabase.instance;
    localDB.dropDB(recreateDB: true).then((_){
      print('DB recreated!');
    }).then((_) {
      _insertInitialData();
      print('_insertInitialData done');
    }).then(() {
      _insertAdditionalData();
      print('_insertAdditionalData done');
    });
  } catch (ex) {
    print('There was a problem in populateDB(): $ex');
  }
}

CodePudding user response：

Cool. Thanks for your comments. I replaced all of those Future.wait for async/await even in my internal methods that insert into the DB and it's all good!!! (executing in the sequence I need)

Just learning Dart/Flutter for fun and I love it.