geo_sort 0.2.0

A Dart package for sorting a list of geographic locations based on their distance from a reference location.

geo_sort

A Flutter package for sorting a list of geographic locations based on their distance from a reference point.

Supports both Haversine (fast, < 0.3% error) and Vincenty (accurate to 0.5 mm on WGS-84) distance algorithms via latlong2.

Installation

Add to your pubspec.yaml:

dependencies:
  geo_sort: ^0.2.0

Then run:

flutter pub get

Usage

1. Implement HasLocation

Any model class needs to implement the HasLocation interface by exposing latitude and longitude:

import 'package:geo_sort/geo_sort.dart';

class City implements HasLocation {
  final String name;
  @override
  final double? latitude;
  @override
  final double? longitude;

  City({required this.name, required this.latitude, required this.longitude});
}

2. Sort by distance

final cities = [
  City(name: 'Rome',   latitude: 41.9028, longitude: 12.4964),
  City(name: 'Milan',  latitude: 45.4642, longitude: 9.1900),
  City(name: 'Naples', latitude: 40.8518, longitude: 14.2681),
];

final sorted = GeoSort.sortByLatLong(
  items: cities,
  latitude: 41.9028,   // reference point
  longitude: 12.4964,
);
// → [Rome, Naples, Milan]

Parameters

Parameter	Type	Default	Description
items	List<T>	required	List of items to sort
latitude	double	required	Reference latitude
longitude	double	required	Reference longitude
ascending	bool	true	Sort direction
maxDistance	double?	null	Max distance in km; items beyond this are excluded
maxElements	int?	null	Max number of items to return
algorithm	GeoDistanceAlgorithm	.haversine	Distance formula to use

Distance algorithms

// Haversine — default, faster
GeoSort.sortByLatLong(
  items: cities,
  latitude: 41.9028,
  longitude: 12.4964,
);

// Vincenty — more precise (accurate to ~0.5 mm on WGS-84 ellipsoid)
GeoSort.sortByLatLong(
  items: cities,
  latitude: 41.9028,
  longitude: 12.4964,
  algorithm: GeoDistanceAlgorithm.vincenty,
);

Advanced example

final nearby = GeoSort.sortByLatLong<City>(
  items: cities,
  latitude: 41.9028,
  longitude: 12.4964,
  ascending: true,
  maxDistance: 300,   // only cities within 300 km
  maxElements: 5,     // return at most 5 results
  algorithm: GeoDistanceAlgorithm.vincenty,
);

Contributing

Issues and pull requests are welcome at github.com/mariorefetto/geo_sort.

License

geo_sort is available under the MIT license. See the LICENSE file for details.