Dart non-async function return wait until for loop is complete - flutter

Question

Here is my code
List<DocumentReference> getStacks(
List<DocumentReference> favoritePlayers,
List<DocumentReference> stacks,
) {
List<DocumentReference> newStacks = [];
for (var i = 0; i < stacks.length; i++) {
stacks[i].get().then((DocumentSnapshot stackSnapshot) {
if (stackSnapshot.exists) {
DocumentReference thisstack = stackSnapshot['player'];
for (var x = 0; x < favoritePlayers.length; x++) {
if (favoritePlayers[x] == thisstack) {
newStacks.add(stacks[i]);
}
}
}
});
if (stacks.length - 1 == i) {
return newStacks;
}
}
}
I do not have the option in the platform I am using to make the function async or Future, so I am trying to figure out a way to not return until both for loops are done. I have tried while loops and do while, but I guess I am missing something, this method is close, but it seems it still finishes before the inner loop does and wants to return nothing.
Any thoughts would be great.

Answer 1

In your code, the loop goes to the next operation without waiting for "stacks[i].get()" .
If the "stacks[i].get()" function is not a Future function, you can use it as follows.
List getStacks( List favoritePlayers, List stacks) {
List newStacks = [];
for (final stack in stacks) {
DocumentSnapshot stackSnapshot = stack.get();
//code
newStacks.add(stackSnapshot);
}
return newStacks;
}
If it is a future function, it should be like this;
Future<List> getStacks( List favoritePlayers, List stacks) async{
List newStacks = [];
for (final stack in stacks) {
DocumentSnapshot stackSnapshot = await stack.get();
//code
newStacks.add(stackSnapshot);
}
return newStacks;
}