trackoffical_app/lib/model/distance.dart

import 'package:trackoffical_app/service/service.dart';

class Distance {
  // Fast path internal direct constructor to avoids the optional arguments
  // and [_km] recomputation.
  // The `+ 0` prevents -0.0 on the web, if the incoming duration happens to be -0.0.
  const Distance._km(double distance) : _valueKm = distance + 0;

  const Distance(
      {double km = 0,
        double m= 0}):this._km(km + m/ 1000);

  /// Adds this Duration and [other] and
  /// returns the sum as a new Duration object.
  Distance operator +(Distance other) {
    return Distance._km(_valueKm + other._valueKm);
  }

  /// Subtracts [other] from this Duration and
  /// returns the difference as a new Duration object.
  Distance operator -(Distance other) {
    return Distance._km(_valueKm - other._valueKm);
  }

  /// Multiplies this Duration by the given [factor] and returns the result
  /// as a new Duration object.
  ///
  /// Note that when [factor] is a double, and the duration is greater than
  /// 53 bits, precision is lost because of double-precision arithmetic.
  Distance operator *(num factor) {
    return Distance._km(_valueKm * factor);
  }
  Distance operator /(num factor) {
    return Distance._km(_valueKm / factor);
  }

  /// Whether this [Distance] is shorter than [other].
  bool operator <(Distance other) => _valueKm < other._valueKm;

  /// Whether this [Distance] is longer than [other].
  bool operator >(Distance other) => _valueKm > other._valueKm;

  /// Whether this [Distance] is shorter than or equal to [other].
  bool operator <=(Distance other) => _valueKm <= other._valueKm;

  /// Whether this [Distance] is longer than or equal to [other].
  bool operator >=(Distance other) => _valueKm >= other._valueKm;


  final double _valueKm;

  double get km => _valueKm;
  double get m => _valueKm*1000;

  (String, String) toStringValueAndUnit({int fixed=1}) {
    if (_valueKm < 1) {
      return ('${m.round()}', 'm');
    } else {
      return ((km.toStringAsFixed(fixed)), 'km');
    }
  }
  @override
  String toString(){
    final (v, u) = toStringValueAndUnit(fixed: 1);
    return '$v $u';
  }
}