rshankras/geotoolbox

GeoToolbox and PlaceDescriptor Patterns

Portable location representation using PlaceDescriptor from the GeoToolbox framework. Covers place construction from coordinates, addresses, and MapKit items; forward and reverse geocoding with the new async APIs; and multi-service place identifiers for cross-platform interop.

When This Skill Activates

Use this skill when the user:

• Asks about GeoToolbox or PlaceDescriptor
• Wants to represent a place with coordinates, address, or common name
• Needs to convert between MKMapItem and PlaceDescriptor
• Asks about forward geocoding (address to coordinates) or reverse geocoding (coordinates to address)
• Wants to store or transmit multi-service place identifiers (Apple Maps, Google Maps, etc.)
• Mentions PlaceRepresentation, SupportingPlaceRepresentation, or MKGeocodingRequest
• Asks about portable or interoperable location data structures

Decision Tree

What do you need?
|
+-- Represent a place with coordinates and/or address
|   +-- From a known coordinate
|   |   +-- PlaceRepresentation.coordinate(CLLocationCoordinate2D)
|   +-- From a known address string
|   |   +-- PlaceRepresentation.address(String)
|   +-- Both coordinate and address
|   |   +-- Pass multiple representations to PlaceDescriptor
|   +-- From an existing MKMapItem
|       +-- PlaceDescriptor(item: MKMapItem)
|
+-- Geocode an address to coordinates
|   +-- MKGeocodingRequest(addressString:)
|   +-- try await request.mapItems
|
+-- Reverse geocode coordinates to an address
|   +-- MKReverseGeocodingRequest(location:)
|   +-- try await request.mapItems
|
+-- Attach service identifiers (Apple Maps, Google, etc.)
|   +-- SupportingPlaceRepresentation.serviceIdentifiers([String: String])
|
+-- Read place properties
    +-- descriptor.coordinate, descriptor.address, descriptor.commonName
    +-- descriptor.serviceIdentifier(for: "com.apple.maps")

API Availability

| API | Minimum OS | Import | |-----|-----------|--------| | PlaceDescriptor | iOS 26 / macOS 26 | GeoToolbox | | PlaceRepresentation | iOS 26 / macOS 26 | GeoToolbox | | SupportingPlaceRepresentation | iOS 26 / macOS 26 | GeoToolbox | | MKGeocodingRequest | iOS 26 / macOS 26 | MapKit | | MKReverseGeocodingRequest | iOS 26 / macOS 26 | MapKit | | PlaceDescriptor(item:) | iOS 26 / macOS 26 | GeoToolbox + MapKit | | MKMapItem | iOS 6 / macOS 10.9 | MapKit | | CLLocationCoordinate2D | iOS 2 / macOS 10.6 | CoreLocation |

Quick Start

Create a PlaceDescriptor from Coordinates

import GeoToolbox
import CoreLocation

let coordinate = CLLocationCoordinate2D(latitude: 37.3349, longitude: -122.0090)

let descriptor = PlaceDescriptor(
    representations: [.coordinate(coordinate)],
    commonName: "Apple Park"
)

// Read back
if let coord = descriptor.coordinate {
    print("Lat: \(coord.latitude), Lon: \(coord.longitude)")
}
print(descriptor.commonName ?? "No name")

Create a PlaceDescriptor from an Address

import GeoToolbox

let descriptor = PlaceDescriptor(
    representations: [.address("One Apple Park Way, Cupertino, CA 95014")],
    commonName: "Apple Park"
)

if let address = descriptor.address {
    print("Address: \(address)")
}

Multiple Representations and Service Identifiers

import GeoToolbox
import CoreLocation

let coordinate = CLLocationCoordinate2D(latitude: 37.3349, longitude: -122.0090)

let descriptor = PlaceDescriptor(
    representations: [
        .coordinate(coordinate),
        .address("One Apple Park Way, Cupertino, CA 95014")
    ],
    commonName: "Apple Park",
    supportingRepresentations: [
        .serviceIdentifiers([
            "com.apple.maps": "apple-maps-id-12345",
            "com.google.maps": "ChIJ-bfVTh8_j4ARDMPaL2Njo3I"
        ])
    ]
)

// Access a specific service identifier
if let appleId = descriptor.serviceIdentifier(for: "com.apple.maps") {
    print("Apple Maps ID: \(appleId)")
}

Convert from MKMapItem

import GeoToolbox
import MapKit

func descriptorFromMapItem(_ mapItem: MKMapItem) -> PlaceDescriptor {
    PlaceDescriptor(item: mapItem)
}

Forward Geocoding (Address to Coordinates)

import MapKit

func geocodeAddress(_ addressString: String) async throws -> [MKMapItem] {
    let request = MKGeocodingRequest(addressString: addressString)
    let mapItems = try await request.mapItems
    return mapItems
}

// Usage
let items = try await geocodeAddress("One Apple Park Way, Cupertino, CA")
if let first = items.first {
    let coord = first.placemark.coordinate
    print("Found: \(coord.latitude), \(coord.longitude)")
}

Reverse Geocoding (Coordinates to Address)

import MapKit
import CoreLocation

func reverseGeocode(_ coordinate: CLLocationCoordinate2D) async throws -> [MKMapItem] {
    let location = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
    let request = MKReverseGeocodingRequest(location: location)
    let mapItems = try await request.mapItems
    return mapItems
}

// Usage
let coordinate = CLLocationCoordinate2D(latitude: 37.3349, longitude: -122.0090)
let items = try await reverseGeocode(coordinate)
if let first = items.first {
    print("Address: \(first.placemark.title ?? "Unknown")")
}

Full Integration Example

Geocode an address, convert the result to a PlaceDescriptor with service identifiers, and read back all properties:

import GeoToolbox
import MapKit
import CoreLocation

func buildPlaceDescriptor(from addressString: String) async throws -> PlaceDescriptor? {
    // Forward geocode
    let request = MKGeocodingRequest(addressString: addressString)
    let mapItems = try await request.mapItems
    guard let mapItem = mapItems.first else { return nil }

    // Convert MKMapItem to PlaceDescriptor
    var descriptor = PlaceDescriptor(item: mapItem)

    // Or build manually with extra data
    let coordinate = mapItem.placemark.coordinate
    descriptor = PlaceDescriptor(
        representations: [
            .coordinate(coordinate),
            .address(addressString)
        ],
        commonName: mapItem.name,
        supportingRepresentations: [
            .serviceIdentifiers([
                "com.apple.maps": "resolved-id-\(coordinate.latitude)"
            ])
        ]
    )

    return descriptor
}

func displayDescriptor(_ descriptor: PlaceDescriptor) {
    if let name = descriptor.commonName {
        print("Name: \(name)")
    }
    if let coord = descriptor.coordinate {
        print("Coordinate: \(coord.latitude), \(coord.longitude)")
    }
    if let address = descriptor.address {
        print("Address: \(address)")
    }
    if let appleId = descriptor.serviceIdentifier(for: "com.apple.maps") {
        print("Apple Maps ID: \(appleId)")
    }
}

Top Mistakes

| # | Mistake | Problem | Fix | |---|---------|---------|-----| | 1 | Importing only MapKit when using PlaceDescriptor | PlaceDescriptor lives in GeoToolbox, not MapKit | Add import GeoToolbox alongside import MapKit | | 2 | Using CLGeocoder instead of MKGeocodingRequest | CLGeocoder returns CLPlacemark which lacks MapKit integration | Use MKGeocodingRequest / MKReverseGeocodingRequest for MKMapItem results | | 3 | Assuming PlaceDescriptor always has a coordinate | A descriptor can be address-only with no coordinate | Check descriptor.coordinate for nil before use | | 4 | Assuming PlaceDescriptor always has an address | A descriptor can be coordinate-only with no address | Check descriptor.address for nil before use | | 5 | Hardcoding service identifier keys | Service identifier keys are strings; typos cause silent failures | Define constants for service keys like "com.apple.maps" | | 6 | Passing CLLocationCoordinate2D directly to MKReverseGeocodingRequest | The initializer takes a CLLocation, not a raw coordinate | Wrap in CLLocation(latitude:longitude:) first | | 7 | Ignoring empty geocoding results | Geocoding can return zero results for ambiguous or invalid input | Guard against empty mapItems arrays | | 8 | Not handling geocoding errors | Network or service failures throw errors | Use do/catch or try await with proper error handling |

Patterns

Service Identifier Constants

Define constants to avoid typos in service identifier keys:

// Good -- constants prevent typos
enum PlaceService {
    static let appleMaps = "com.apple.maps"
    static let googleMaps = "com.google.maps"
    static let foursquare = "com.foursquare"
}

if let id = descriptor.serviceIdentifier(for: PlaceService.appleMaps) {
    // use id
}

// Bad -- raw string literals are error-prone
if let id = descriptor.serviceIdentifier(for: "com.apple.map") { // typo: "map" not "maps"
    // silently nil
}

Nil-Safe Property Access

// Good -- check each optional property
func formatPlace(_ descriptor: PlaceDescriptor) -> String {
    var parts: [String] = []
    if let name = descriptor.commonName {
        parts.append(name)
    }
    if let address = descriptor.address {
        parts.append(address)
    }
    if let coord = descriptor.coordinate {
        parts.append("\(coord.latitude), \(coord.longitude)")
    }
    return parts.joined(separator: " -- ")
}

// Bad -- force-unwrapping optional properties
let name = descriptor.commonName! // crashes if nil
let coord = descriptor.coordinate! // crashes if no coordinate representation

Geocoding with Fallback

// Good -- handle empty results and errors
func resolvePlace(_ address: String) async -> PlaceDescriptor? {
    do {
        let request = MKGeocodingRequest(addressString: address)
        let items = try await request.mapItems
        guard let item = items.first else {
            print("No results for address: \(address)")
            return nil
        }
        return PlaceDescriptor(item: item)
    } catch {
        print("Geocoding failed: \(error.localizedDescription)")
        return nil
    }
}

// Bad -- no error handling, no empty check
func resolvePlace(_ address: String) async -> PlaceDescriptor {
    let request = MKGeocodingRequest(addressString: address)
    let items = try! await request.mapItems // crashes on failure
    return PlaceDescriptor(item: items.first!) // crashes if empty
}

Review Checklist

• [ ] import GeoToolbox is present when using PlaceDescriptor, PlaceRepresentation, or SupportingPlaceRepresentation
• [ ] import MapKit is present when using MKGeocodingRequest, MKReverseGeocodingRequest, or MKMapItem
• [ ] import CoreLocation is present when using CLLocationCoordinate2D or CLLocation
• [ ] PlaceDescriptor properties (coordinate, address, commonName) are checked for nil before use
• [ ] Service identifier keys use defined constants, not raw string literals
• [ ] MKReverseGeocodingRequest receives a CLLocation, not a raw CLLocationCoordinate2D
• [ ] Geocoding results are checked for empty arrays before accessing elements
• [ ] Geocoding calls use proper async/await error handling with do/catch
• [ ] Multiple representations are provided when both coordinate and address are known
• [ ] Supporting representations include service identifiers when cross-service interop is needed

Cross-References

• For MapKit map views and annotations, see MapKit documentation
• For CoreLocation permissions and location updates, see CoreLocation documentation
• For SwiftUI integration with maps, see Map view in SwiftUI

References

• GeoToolbox Framework
• PlaceDescriptor
• MKGeocodingRequest
• MKReverseGeocodingRequest
• MKMapItem