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Flutter – Is there a way for a function to return non nullable value even if it has possibility to return one?

I am calling a simple function that returns a duration object. However, it is null at times. I want to modify the code so that it can return only a duration object and not duration? object.

  factory ExecutionModel.fromSnapshot(
      DocumentSnapshot<Map<String, dynamic>> snapshot) {
    final data = snapshot.data()!;
    return ExecutionModel(
        selfRef: snapshot.reference,
        state: TimerState.fromString(data['state']),
        timeAdded: fromJsonDuration(data['duration'] as int), // this line
        activeTimerRef: data['activeTimerRef'],
        paused: fromJsonDateTime(data['paused'] as Timestamp),
        started: fromJsonDateTime(data['started'] as Timestamp));

Duration fromJsonDuration(int milliseconds) {
  return Duration(milliseconds: milliseconds);
}


Here timeAdded argument is a Duration object and not Duration? object. But it can occasionally have null values. What is the fix around for this? I don't want to change timeAdded to Duration? as it can affect other areas.
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3

Answers


  1. 0

    Try this method –

    factory ExecutionModel.fromSnapshot(
      DocumentSnapshot<Map<String, dynamic>> snapshot) {
    final data = snapshot.data()!;
    return ExecutionModel(
        selfRef: snapshot.reference,
        state: TimerState.fromString(data['state']),
        timeAdded: fromJsonDuration(data['duration'] ?? 0),// <== Use this instead it will pass zero to your funcation if  data['duration'] is Null
        activeTimerRef: data['activeTimerRef'],
        paused: fromJsonDateTime(data['paused'] as Timestamp),
        started: fromJsonDateTime(data['started'] as Timestamp));
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  2. 0

    Better solution:

    factory ExecutionModel.fromSnapshot(
      DocumentSnapshot<Map<String, dynamic>> snapshot) {
    final data = snapshot.data()!;
    return ExecutionModel(
        selfRef: snapshot.reference,
        state: TimerState.fromString(data['state']),
        timeAdded: data['duration'] != null ? fromJsonDuration(data['duration']) 
                  : const Duration({your default duration});
        activeTimerRef: data['activeTimerRef'],
        paused: fromJsonDateTime(data['paused'] as Timestamp),
        started: fromJsonDateTime(data['started'] as Timestamp));
    Login or Signup to reply.
  3. 0

    Try this

    Duration fromJsonDuration(int? milliseconds) {
  if (milliseconds != null) {
    return Duration(milliseconds: milliseconds);
  } else {
    return Duration.zero; // or any other default value.
  }
}
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