Refactoring a list of map objects in Dart?

Question

How can this list of map objects be refactored for better reading?

The goal is to have a list variable that stores the x and y values for a couple of points in a compact way. It does not have to be a list of map objects, I just found it the most suitable at the time of writing.

final List<Map<String, double>> _positions = [
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 1,
    'y': _height * 0.120
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 2,
    'y': _height * 0.075
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 3,
    'y': _height * 0.095
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 4,
    'y': _height * 0.070
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 5,
    'y': _height * 0.085
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 6,
    'y': _height * 0.055
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 7,
    'y': _height * 0.060
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 8,
    'y': _height * 0.060
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 9,
    'y': _height * 0.045
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 10,
    'y': _height * 0.025
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 11,
    'y': _height * 0.04
  },
  {
    'x': _offsetCircle + _circleDistanceHorizontal * 12,
    'y': _height * 0.005
  }
];

Axot · Accepted Answer · 2020-05-12 21:27:34Z

2

    final items = [0.12, 0.075, 0.095];
  List<Map<String, double>> result = List<Map<String, double>>.generate(items.length ,(index) {
    return {
      'x': _offsetCircle + _circleDistanceHorizontal * (index + 1), 
      'y':_height * items[index]
     };
  });

answered May 12, 2020 at 21:27

Axot

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2 Comments

Christopher Moore Over a year ago

You should provide some explanation for this code as well.

Heikkisorsa Over a year ago

Thanks, that helps. Is even an easier way in Dart to make such an ordered set of tuples?

Eiko · Accepted Answer · 2020-05-13 09:40:25Z

1

The answer of @Axot is good. I think you might want to improve on the stored data structure as well. If you are storing coordinates, maybe just create a Point class.

class Point {
  final double x;
  final double y;

  Point(this.x, this.y);
}

double _offsetCircle = 1.0, _circleDistanceHorizontal = 1.0;
double _height = 1.0;
final factors = [0.120, 0.075, 0.095];

final list = Iterable<int>.generate(factors.length)
    .map((i) => Point(_offsetCircle + _circleDistanceHorizontal * (i + 1),
        _height * factors[i]))
    .toList();

answered May 13, 2020 at 9:40

Eiko

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