SwiftyH3 ⬡

November 22, 2025 · View on GitHub

The Swifty way to use Uber's H3 geospatial indexing system.

Quick Start

import SwiftyH3

// Find the containing cell for a given location
let latlng = H3LatLng(latitudeDegs: 37.7955, longitudeDegs: -122.3937)
let cell = try! latlng.cell(at: .res10)
print(cell) // 8a283082a677fff

// Retrieve the center of the cell (as H3LatLng or CLLocationCoordinate2D)
let coordinate: CLLocationCoordinate2D = try! cell.center.coordinates

// Find the bounds of this cell
let bounds: [H3LatLng] = try! cell.boundary

Installation

Swift Package Manager

Add the following line to your package's Package.swift file:

.package(url: "https://github.com/pawelmajcher/SwiftyH3.git", "0.5.0"..<"0.6.0")

Xcode

Go to File > Add Package Dependencies... and enter https://github.com/pawelmajcher/SwiftyH3.git in the upper-right corner.

H3 API support

Indexing functions

H3 C function	Example SwiftyH3 code	Docs
`latLngToCell`	`try H3LatLng(latitudeDegs: 37.7955, longitudeDegs: -122.3937).cell(at: .res8)`	📖
`cellToLatLng`	`try H3Cell("8a283082a677fff")!.center`	📖
`cellToBoundary`	`try H3Cell("8a283082a677fff")!.boundary`	📖

Index inspection functions

H3 C function	Example SwiftyH3 code	Docs
`getResolution`	`try H3DirectedEdge("115283473fffffff")!.resolution`	📖
`getBaseCellNumber`	`try H3Vertex("22528340bfffffff")!.baseCellNumber`	📖
`getIndexDigit`	`try H3Vertex("22528340bfffffff")!.digit(for: .res2)`	📖
`constructCell`	`try H3Cell(base: 20, [0, 6, 0, 4, 0, 5])`	📖
`stringToH3`	`H3Cell("8a283082a677fff")!`	📖
`h3ToString`	`try H3Cell(599686042433355775).description`	📖
`isValidCell`	`cell.isValid`	📖
`isValidIndex`	`cell.isSomeH3Index`	📖
`isResClassIII`	`cell.isResClassIII`	📖
`isPentagon`	`cell.isPentagon`	📖
`getIcosahedronFaces`	⚠️ Not yet available
`maxFaceCount`	This function exists for memory management and is not exposed.

Grid traversal functions

H3 C function	Example SwiftyH3 code	Docs
`gridDistance`	`try originCell.gridDistance(to: destinationCell)`	📖
`gridRing`	`try cell.gridRing(distance: 1)`	📖
`gridRingUnsafe`	Not exposed. Use `gridRing`.
`maxGridRingSize`	This function exists for memory management and is not exposed.
`gridDisk`	`try cell.gridDisk(distance: 2)`	📖
`maxGridDiskSize`	This function exists for memory management and is not exposed.
`gridDiskDistances`	Not exposed. Use `try 1...3.map { cell.gridRing(distance: \$0) }`.
`gridDiskUnsafe`	Not exposed. Use `gridDisk`.
`gridDiskDistancesUnsafe`	Not exposed. Use `try 1...3.map { cell.gridRing(distance: \$0) }`.
`gridDiskDistancesSafe`	Not exposed. Use `try 1...3.map { cell.gridRing(distance: \$0) }`.
`gridDisksUnsafe`	Not exposed. Use `try cells.flatMap { cell in 1...3.flatMap { cell.gridRing(distance: \$0) } }`.
`gridPathCells`	`try cell1.path(to: ...)`	📖
`gridPathCellsSize`	This function exists for memory management and is not exposed.
`cellToLocalIj`	⚠️ Not yet available
`localIjToCell`	⚠️ Not yet available

Hierarchical grid functions

H3 C function	Example SwiftyH3 code	Docs
`cellToParent`	`try cell.parent(at: .res1)`	📖
`cellToChildren`	`try cell.children(at: .res12)`	📖
`cellToChildrenSize`	`try cell.children(at: .res12).count`	📖
`cellToCenterChild`	`try cell.children(at: .res12).center`	📖
`cellToChildPos`	`try parentCell.children(at: .res12).index(of: childCell)`	📖
`childPosToCell`	`try cell.children(at: .res12)[23]`	📖
`compactCells`	`try [cell1, ..., cell50].compacted`	📖
`uncompactCells`	`try [cell1, cell2, cell3].uncompacted(at: .res8)`	📖
`uncompactCellsSize`	This function exists for memory management and is not exposed.

Region functions

H3 C function	Example SwiftyH3 code	Docs
`polygonToCells`	`try H3Polygon([...]).cells(at: .res7)`	📖
`maxPolygonToCellsSize`	This function exists for memory management and is not exposed.
`polygonToCellsExperimental`	`try H3Polygon([...]).cellsExperimental(at: .res7, containmentType: .overlapping)`	📖
`maxPolygonToCellsSizeExperimental`	This function exists for memory management and is not exposed.
`cellsToLinkedMultiPolygon`	`try [cell1, cell2, cell3].multiPolygon`	📖
`destroyLinkedMultiPolygon`	This function exists for memory management and is not exposed.

Directed edge functions

H3 C function	Example SwiftyH3 code	Docs
`areNeighborCells`	`try cell1.isNeighbor(of: cell2)`	📖
`cellsToDirectedEdge`	`try originCell.directedEdge(to: destinationCell)`	📖
`isValidDirectedEdge`	`directedEdge.isValid`	📖
`getDirectedEdgeOrigin`	`try directedEdge.origin`	📖
`getDirectedEdgeDestination`	`try directedEdge.destination`	📖
`directedEdgeToCells`	Not exposed. Use `try (directedEdge.origin, directedEdge.destination)`.
`originToDirectedEdges`	`try originCell.directedEdges`	📖
`directedEdgeToBoundary`	`try directedEdge.boundary`	📖

Vertex functions

H3 C function	Example SwiftyH3 code	Docs
`cellToVertex`	`try cell.vertex(3)`	📖
`cellToVertexes`	`try cell.vertices`	📖
`vertexToLatLng`	`try vertex.latLng`	📖
`isValidVertex`	`vertex.isValid`	📖

Miscellaneous H3 functions

H3 C function	Example SwiftyH3 code	Docs
`degsToRads`	Not exposed. Use `Measurement<UnitAngle>(value: 23, unit: .degrees).converted(to: .radians).value`.
`radsToDegs`	Not exposed. Use `Measurement<UnitAngle>(value: 1.2, unit: .radians).converted(to: .degrees).value`.
`getHexagonAreaAvgKm2`	`H3Cell.Resolution.res8.averageHexagonArea.converted(to: .squareKilometers).value`
`getHexagonAreaAvgM2`	`H3Cell.Resolution.res8.averageHexagonArea.value`	📖
`cellAreaRads2`	`try cell.areaRads2`	📖
`cellAreaKm2`	`try cell.area.converted(to: .squareKilometers).value`
`cellAreaM2`	`try cell.area.converted(to: .squareMeters).value`	📖
`getHexagonEdgeLengthAvgKm`	`H3Cell.Resolution.res8.averageHexagonEdgeLength.converted(to: .kilometers).value`
`getHexagonEdgeLengthAvgM`	`H3Cell.Resolution.res8.averageHexagonEdgeLength.value`	📖
`edgeLengthKm`	`try directedEdge.length.converted(to: .kilometers).value`
`edgeLengthM`	`try directedEdge.length.value`	📖
`edgeLengthRads`	`try directedEdge.lengthRads.value`	📖
`getNumCells`	`H3Cell.Resolution.res3.numberOfCells`	📖
`getRes0Cells`	`H3Cell.res0Cells`	📖
`res0CellCount`	This function exists for memory management and is not exposed.
`getPentagons`	`H3Cell.Resolution.res3.pentagons`	📖
`pentagonCount`	This function exists for memory management and is not exposed.
`greatCircleDistanceKm`	`h3LatLng1.distance(to: h3LatLng2).converted(to: .kilometers).value`
`greatCircleDistanceM`	`h3LatLng1.distance(to: h3LatLng2).value`	📖
`greatCircleDistanceRads`	`h3LatLng1.distanceRads(to: h3LatLng2).value`	📖
`describeH3Error`	`do {...} catch { print(error.errorDescription) }`	📖

Note

The Measurement<UnitType> types and LocalizedError protocol, including related methods and properties, are part of Foundation. Include import Foundation to use them.

Core Location and MapKit support

CLLocationCoordinate2D

You can convert an H3LatLng value to CLLocationCoordinate2D and vice versa using initializers or computed properties.

// H3LatLng ➡️ CLLocationCoordinate2D
let coordinateFromProperty: CLLocationCoordinate2D = H3LatLng(latitudeDegs: 37.7955, longitudeDegs: -122.3937).coordinates
let coordinateFromInitializer = CLLocationCoordinate2D(H3LatLng(latitudeDegs: 37.7955, longitudeDegs: -122.3937))

// CLLocationCoordinate2D ➡️ H3LatLng
let h3LatLngFromProperty: H3LatLng = CLLocationCoordinate2D(latitude: 37.7955, longitude: -122.3937).h3LatLng
let h3LatLngFromInitializer = H3LatLng(CLLocationCoordinate2D(latitude: 37.7955, longitude: -122.3937))

MKPolygon and MKMultiPolygon

You can create an MKPolygon with an initializer taking [H3LatLng] or H3Polygon values. Analogically, you can initialize MKMultiPolygon with [H3Polygon] array.

// H3 with MapKit for SwiftUI example

import SwiftUI
import MapKit
import SwiftyH3

struct H3CellMapExampleView: View {
    let cellBoundary = try! H3LatLng(latitudeDegs: 37.7955, longitudeDegs: -122.3937).cell(at: .res4).boundary
    
    var body: some View {
        Map {
            MapPolygon(MKPolygon(cellBoundary))
        }
    }
}

MapContent (MapKit for SwiftUI)

H3Cell, H3Polygon, and H3DirectedEdge conform to the MapContent protocol which means that you can use them as map content when using MapKit for SwiftUI.

// H3 with MapKit for SwiftUI example

import SwiftUI
import MapKit
import SwiftyH3

struct H3CellMapExampleView: View {
    var body: some View {
        Map {
            H3Cell("87283082affffff")
            H3DirectedEdge("115283473fffffff").stroke(.blue, lineWidth: 2)
            try? ["8528342ffffffff", "85283093fffffff"].map { H3Cell(\$0)! }.multiPolygon[0]
        }
    }
}

License

SwiftyH3 (this repository) is licensed under the Apache 2.0 license.
Uber's H3 library is licensed under the Apache 2.0 license.