Swift Google Polylines

Google's direction API provides points along route segments as an encoded string. For example the encoded string:

_p~iF~ps|U_ulLnnqC_mqNvxq`@

decodes to the coordinate points:

(38.5, -120.2), (40.7, -120.95), (43.252, -126.453)

Full details of the algorithm used can be found here.

The Swift extensions provided here support encoding and decoding to and from the String and MKPolyline classes.

Usage

Examples of usage

Decoding

Decoding throws GooglePolylineError.InvalidPolylineString if the string is not a valid Google polyline.

let googlePolyline = "`_p~iF~ps|U_ulLnnqC_mqNvxq`@"

// Get lazy sequence of CLLocationCoordinate2D 
let seq = try googlePolyline.makeCoordinateSequenceFromGooglePolyline()

// Get array of CLLocationCoordinate2D
let array = try googlePolyline.makeCoordinateArrayFromGooglePolyline()

// Get MKPolyline
let polyline = try googlePolyline.makeMKPolylineFromGooglePolyline()
let anotherPolyline = try MKPolyline(encodedGooglePolyline:googlePolyline)

Encoding

let googlePolyline = "`_p~iF~ps|U_ulLnnqC_mqNvxq`@"
let polyline = MKPolyline(encodedGooglePolyline:googlePolyline)
let points = [
    CLLocationCoordinate2D(latitude: 38.5, longitude: -120.2),
    CLLocationCoordinate2D(latitude: 40.7, longitude: -120.95),
    CLLocationCoordinate2D(latitude: 43.252, longitude: -126.453)
]

// Encode from sequence of CLLocationCoordinate2D
let encodedFromPoints = String(googlePolylineLocationCoordinateSequence:points)

// Encode from sequence of MKMapPoint
let encodedFromMapPoints = String(googlePolylineMapPointSequence:
	points.map { MKMapPointForCoordinate($0) })

// Encode from MKPolyline
let encodedFromPolyline = String(googlePolylineMKPolyline:polyline)
let anotherEncodedFromPolyline = polyline.googlePolyline

Credits

This library has been created by Mark Woollard and has been made available under the MIT License. Please see the LICENSE file for more information.