Instead of storing full GeoJSON strings, convert to MKPolygon coordinates and serialize as [CLLocationCoordinate2D] using NSKeyedArchiver . This reduces retrieval latency by 70%.
| Level | Without Compression | With TopoJSON + ZIP | |-------|--------------------|----------------------| | World (all 4000 provinces) | 420 MB | 118 MB | | Single large country (e.g., China 34 provinces) | 18 MB | 4.2 MB | | Small country (e.g., Belgium 10 provinces) | 1.2 MB | 0.3 MB | World Provinces Download Ios
Use a bounding box pre-filter then point-in-polygon (PIP) on the retrieved polygon. For 5000+ provinces, implement a grid index. Instead of storing full GeoJSON strings, convert to
func findProvince(at coordinate: CLLocationCoordinate2D) -> Province? let bboxPredicate = NSPredicate(format: "minLat <= %f AND maxLat >= %f AND minLon <= %f AND maxLon >= %f", ...) let candidates = try! context.fetch(Province.fetchRequest(with: bboxPredicate)) return candidates.first $0.polygon.contains(coordinate) For 5000+ provinces, implement a grid index
(Hypothetical) github.com/example/WorldProvincesiOS
func savePolygon(_ polygon: MKPolygon, for provinceID: String) let coordData = try? NSKeyedArchiver.archivedData(withRootObject: polygon.coordinates, requiringSecureCoding: true) provinceEntity.boundaryData = coordData