Using value types with MKMapView

This project is an addition to annotation binding enabling value types (such as structs, enums) as MKMapView annotations.

Background

As MKMapView enforces annotations to conform to NSObjectProtocol a developer has pretty much no other choice other than make annotations derive from NSObject in his project. However, these reference types are good to be avoided when dealing with Rx and thus the goal of this project is to make value type binding possible.

Usage

You need a custom type and an annotation wrapper for it:

/// A custom type to be bound to the map.
struct PointOfInterest: IdentifiableAnnotation {

    var annotationID = UUID()
    let coordinate: CLLocationCoordinate2D
    let title: String?
    let subtitle: String?

    init(title: String, subtitle: String, coordinate: CLLocationCoordinate2D) {
        self.title = title
        self.subtitle = subtitle
        self.coordinate = coordinate
    }
}

/// A subclass of MKAnnotation, to be shown on the map.
class PointOfInterestAnnotation: NSObject, RxAnnotation {

    @objc var coordinate: CLLocationCoordinate2D

    var box: PointOfInterest

    var title: String? {
        return self.box.title
    }

    init(_ annotation: PointOfInterest) {
        self.box = annotation
        self.coordinate = annotation.coordinate
    }

    func update(from annotation: PointOfInterest) {
        self.box = annotation
        self.coordinate = annotation.coordinate
    }
}

With these two types, you create the binding and you're good to go.

    mapView.rx.region
        .withLatestFrom(points) { ($1, $0) }
        .map { (points, region) in points.filter(region.contains(poi:)) }
        .asDriver(onErrorJustReturn: [])
        .drive(mapView.rx.items(create: PointOfInterestAnnotation.init))
        .disposed(by: disposeBag)

In order to get get the selection from the map, you need to use selectedItem(ofMappedType:) which gives you the original type.

    mapView.rx.didSelectItem(ofMappedType: PointOfInterestAnnotation.self)
        .debug("didSelectItem", trimOutput: true)
        .subscribe()
        .disposed(by: disposeBag)

Installation

In order to use this extension, RxMKMapView along with RxSwift and RxCocoa are needed. Just copy the file RxMapAnnotations.swift into your project.