How to set the value of an object inside another list object in the flutter-CodePudding

In my app, I need to get some data and storage them and finally show them in graph. So, I have defined some class as follows: `

class DurationTime {
  StatisticalParam p24H;
  StatisticalParam p1W;
  StatisticalParam p1M;
  StatisticalParam p1GD;
  DurationTime(this.p24H,this.p1W,this.p1M,this.p1GD);// to create getter : Alt Insert
  factory DurationTime.fromMap(Map data) =>  DurationTime(data['p24H'],data['p1W'],data['p1M'],data['p1G']);
}
class StatisticalParam {
  TimeValuePair max;
  TimeValuePair min;
  TimeValuePair avg;
  TimeValuePair latest;
  List<TimeValuePair> timeSeriesData = List<TimeValuePair>.filled(5760,TimeValuePair(0,0));//<TimeValuePair>[];
  StatisticalParam(this.min,this.max,this.avg,this.latest,this.timeSeriesData);

  factory StatisticalParam.fromMap(Map data) => StatisticalParam(data['max'],data['min'],data['avg'],data['latest'],data['timeSeriesData']);
}
class TimeValuePair{
  TimeValuePair(this.value,this.time);
  double value;
  double time;

  factory TimeValuePair.fromMap(Map data) => TimeValuePair(data['value'],data['time']);
}

Then I defined a list with name of instDevice, and initialize it as follow:

List<DurationTime> instDevice = List<DurationTime>.filled(11,
    DurationTime(StatisticalParam(TimeValuePair(0,0), TimeValuePair(0,0), TimeValuePair(0,0), TimeValuePair(0,0),List<TimeValuePair>.filled(5760,TimeValuePair(0,0))),
        StatisticalParam(TimeValuePair(0,0), TimeValuePair(0,0), TimeValuePair(0,0), TimeValuePair(0,0),List<TimeValuePair>.filled(5760,TimeValuePair(0,0))),
        StatisticalParam(TimeValuePair(0,0), TimeValuePair(0,0), TimeValuePair(0,0),TimeValuePair(0,0),List<TimeValuePair>.filled(5760,TimeValuePair(0,0))),
        StatisticalParam(TimeValuePair(0,0), TimeValuePair(0,0), TimeValuePair(0,0),TimeValuePair(0,0),List<TimeValuePair>.filled(5760,TimeValuePair(0,0)))));

When I want to assigne value to

instDevice.elementAt(Index).p24H.latest.value

for Index=1, it is changing for all Index=0 to 11 not only Index=1!! Please let me know, how I can setinstDevice.elementAt(Index).p24H.latest.valuefor specialIndex`?

Please let me know, how I can set instDevice.elementAt(Index).p24H.latest.value for special Index?

CodePudding user response：

Any reason this doesn't work? I might be misunderstanding the issue:

instDevice[index].p24H = newValue;

CodePudding user response：

List.filled will use the same instance for every position. You need a new instance in each position otherwise, yes, you'll update the shared instance in every position. Instead of using List.filled, use List.generate

  List<DurationTime> instDevice = List<DurationTime>.generate(
    11,
    (i) => DurationTime(
      StatisticalParam(
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        List<TimeValuePair>.filled(
          1,
          TimeValuePair(0, 0),
        ),
      ),
      StatisticalParam(
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        List<TimeValuePair>.filled(
          1,
          TimeValuePair(0, 0),
        ),
      ),
      StatisticalParam(
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        List<TimeValuePair>.filled(
          1,
          TimeValuePair(0, 0),
        ),
      ),
      StatisticalParam(
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        TimeValuePair(0, 0),
        List<TimeValuePair>.filled(
          1,
          TimeValuePair(0, 0),
        ),
      ),
    ),
  );