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Address Autocompletion Using SwiftUI and MapKit

by Max KalikMarch 21st, 2023

Too Long; Didn't Read

SwiftUI and MapKit can be used to implement address autocompletion in iOS. The app will have two screens: Content and Map. The first screen will show a map that encloses the search results. The second screen will just show a list of results from the search. Source Code: https://github.com/maxkalik/address-autocomplete-swiftui

featured image - Address Autocompletion Using SwiftUI and MapKit

Surprisingly for myself, I realized that I have never implemented address autocompletion using only Apple technologies. Before, I had experience only with Google Places SDK and even with the not-so-well-known European GeoDataHub. I found it curious — to know how we can limit ourselves to using only SwiftUI and MapKit to solve a similar problem.

MapKit

Before starting let’s briefly describe MapKit — a powerful framework invented by Apple. See documentation:

Display map or satellite imagery within your app, call out points of interest, and determine placemark information for map coordinates.

The framework includes a bunch of useful things. I will list only what we are going to use: the Map itself (

MapView

for SwiftUI);

MKCoordinateRegion

— this model will allow showing a particular region on the map;

MKAnnotation

— another model with coordinates and other data for showing

MapMarker

on the map, and

MKLocalSearch

engine which we are going to use to get a list of completions from searchable address. To implement this we need to

useMKLocalSearchCompleterDelegate

and

MKLocalSearchCompleter

where we can get results — possible addresses.

Project Overview

The completed task should look like this:

We are not going to ask a user to get the current location of a device hence we will not touch

plist

configuration at all, I tried to simplify the project as much as possible. Let’s start with a couple of models. The goal is to see how many things we need to implement for this simple application.

So the structure is the following, MVVM with two screens: Content and Map.

Models

Let’s start with a couple of models:

AddressResult

and

Annotation

. Both should be conformed to

Identifiable

protocol because we are going to use them in the collections.

struct AddressResult: Identifiable {
    let id = UUID()
    let title: String
    let subtitle: String
}

struct AnnotationItem: Identifiable {
    let id = UUID()
    let latitude: Double
    let longitude: Double
    var coordinate: CLLocationCoordinate2D {
        CLLocationCoordinate2D(latitude: latitude, longitude: longitude)
    }
}

AddressResult

model will be used in the list of results.

AnnotationItem

collection we will set right in the Map component. But before dive in into this, let's set up our view models first.

Content View Model

Our iOS application is starting from

ContentView

because we are using SwiftUI, therefore, we need to prepare our first view model:

ContentViewModel

. The

ContentViewModel

will be observable because two things need to be published — the value from

textfield

(searchable text) and results array of

AddressResult

model.

class ContentViewModel: NSObject, ObservableObject {
    
    @Published private(set) var results: Array<AddressResult> = []
    @Published var searchableText = ""

    private lazy var localSearchCompleter: MKLocalSearchCompleter = {
        let completer = MKLocalSearchCompleter()
        completer.delegate = self
        return completer
    }()
    
    func searchAddress(_ searchableText: String) {
        guard searchableText.isEmpty == false else { return }
        localSearchCompleter.queryFragment = searchableText
    }
}

Some of you can notice

searchableText

is not marked as

private(set)

. This is because this value is going to be bound. Also, as you can see, here is an

initializedMKLocalSearchCompleter

. This completer will help to get results using

queryFragment

. For that, we need to conform to the

MKLocalSearchCompleterDelegate

extension ContentViewModel: MKLocalSearchCompleterDelegate {
    func completerDidUpdateResults(_ completer: MKLocalSearchCompleter) {
        Task { @MainActor in
            results = completer.results.map {
                AddressResult(title: $0.title, subtitle: $0.subtitle)
            }
        }
    }
    
    func completer(_ completer: MKLocalSearchCompleter, didFailWithError error: Error) {
        print(error)
    }
}

We are not going to handle errors at this time, so let me skip this part, we can just print a message. The

methodcompleterDidUpdateResults

where results are set from the completer’s results. Since our results are published, so we need to the main thread to avoid this warning:

[SwiftUI] Publishing changes from within view updates is not allowed, this will cause undefined behavior

Map View Model

The view models in this project are independent. We are going to observe them using

@StateObject

. The

MapViewModel

is pretty simple: two published variables and one method:

class MapViewModel: ObservableObject {

    @Published var region = MKCoordinateRegion()
    @Published private(set) var annotationItems: [AnnotationItem] = []
    
    func getPlace(from address: AddressResult) {
        let request = MKLocalSearch.Request()
        let title = address.title
        let subTitle = address.subtitle
        
        request.naturalLanguageQuery = subTitle.contains(title)
        ? subTitle : title + ", " + subTitle
        
        Task {
            let response = try await MKLocalSearch(request: request).start()
            await MainActor.run {
                self.annotationItems = response.mapItems.map {
                    AnnotationItem(
                        latitude: $0.placemark.coordinate.latitude,
                        longitude: $0.placemark.coordinate.longitude
                    )
                }
                
                self.region = response.boundingRegion
            }
        }
    }
}

Region value as

MKCoordinateRegion

will be bound with a view and

AnnotationItem

collection will be used by the Map view itself.

The most interesting part is this

getPlace

method with the argument as

AddressResult

. Briefly, this method converts our row address data into the coordinates using

MKLocalSearch

request!

Our address consists of a title and subtitle. In some cases, subtitle can contain the title, so we need to check first this part to prepare

naturalLanguageQuery

. Next, it is going to be a task with

MKLocalSearch

utility. From the response we need two things:

MapItem

collection and

MKCoordinateRegion

. From the first one, we will prepare

AnnotationItem

collection. The second one will be a map region that encloses the returned search results.

Content View

I really enjoy SwiftUI because you don’t need to spend so much time building user interfaces. It means you will spend really about 10 mins just to implement everything — 2 screens including a map.

Our task is simple, we need to prepare just a

NavigationView

with

TextField

for query and a

List

of results. Let’s take a look:

The first screen is when the app is just launched and the

textfield

is immediately focused on appearing. Also, I couldn’t resist myself to add a clear button to the

TextField

. So, let’s implement all these views.

struct ContentView: View {
    
    @StateObject var viewModel: ContentViewModel
    @FocusState private var isFocusedTextField: Bool
    
    var body: some View {
        NavigationView {
            VStack(alignment: .leading, spacing: 0) {

                TextField("Type address", text: $viewModel.searchableText)
                    .padding()
                    .autocorrectionDisabled()
                    .focused($isFocusedTextField)
                    .font(.title)
                    .onReceive(
                        viewModel.$searchableText.debounce(
                            for: .seconds(1),
                            scheduler: DispatchQueue.main
                        )
                    ) {
                        viewModel.searchAddress($0)
                    }
                    .background(Color.init(uiColor: .systemBackground))
                    .overlay {
                        ClearButton(text: $viewModel.searchableText)
                            .padding(.trailing)
                            .padding(.top, 8)
                    }
                    .onAppear {
                        isFocusedTextField = true
                    }

                List(self.viewModel.results) { address in
                    AddressRow(address: address)
                        .listRowBackground(backgroundColor)
                }
                .listStyle(.plain)
                .scrollContentBackground(.hidden)
            }
            .background(backgroundColor)
            .edgesIgnoringSafeArea(.bottom)
        }
    }
    
    var backgroundColor: Color = Color.init(uiColor: .systemGray6)
}

I will not go through line by line because, in my opinion, this code is pretty simple. I just wanted to grab your attention on some parts.

```
FocusState
```
is used for focusing
```
TextView
```
on appear.
On receiving value in
```
TextView
```
, it’s needed to wait at least 1 second to get a searchable text except by querying each letter.
List view. I tested
```
.scrollContentBackground(.hidden)
```
which works only in iOS16 — it helps to hide a content background.
Using
```
overlay
```
in
```
TextField
```
we can add our
```
ClearButton
```
with bound searchable text (1. for checking if this text is not empty then the clear button will be rendered; 2. for clearing text from the
```
ClearButton
```
component).

struct ClearButton: View {
    
    @Binding var text: String
    
    var body: some View {
        if text.isEmpty == false {
            HStack {
                Spacer()
                Button {
                    text = ""
                } label: {
                    Image(systemName: "multiply.circle.fill")
                        .foregroundColor(Color(red: 0.7, green: 0.7, blue: 0.7))
                }
                .foregroundColor(.secondary)
            }
        } else {
            EmptyView()
        }
    }
}

The Address row is wrapped by

NavigationLink

with a destination in

MapView

struct AddressRow: View {
    
    let address: AddressResult
    
    var body: some View {
        NavigationLink {
            MapView(address: address)
        } label: {
            VStack(alignment: .leading) {
                Text(address.title)
                Text(address.subtitle)
                    .font(.caption)
            }
        }
        .padding(.bottom, 2)
    }
}

Map View

The second screen is a map itself and this view should show the correct location from the search result.

It’s going to be only one view: Map View. As you remember

getPlace

method converts addresses into coordinates, so when the view appears we need to update the coordinates: region and annotation items. Eventually, in annotation content, we can prepare the

MapMarker

. Map view configured with

coordinateRegion

annotationItems

, and

annotationContent

arguments. When all data is ready in the view model, the Map view will be updated. As you can see

coordinateRegion

argument applies a binding value.

annotationItems

can be just identifiable with coordinate variable inside (latitude and longitude) — it’s used in

annotationContent

item in closure.

struct MapView: View {
    
    @StateObject private var viewModel = MapViewModel()

    private let address: AddressResult
    
    init(address: AddressResult) {
        self.address = address
    }
    
    var body: some View {
        Map(
            coordinateRegion: $viewModel.region,
            annotationItems: viewModel.annotationItems,
            annotationContent: { item in
                MapMarker(coordinate: item.coordinate)
            }
        )
        .onAppear {
            self.viewModel.getPlace(from: address)
        }
        .edgesIgnoringSafeArea(.bottom)
    }
}

Btw, when you build the project you might see some SwiftUI warnings: Publishing changes from within view updates is not allowed…— which means you probably updated coordinates during view rendering. If you think that you did absolutely right, your states are updated from

onAppear

, so it can be an issue in Map inside. You can check this article about this issue by Donney Wals.

Wrapping up

Countless applications use Maps. But still few of them use a combination of SwiftUI and MapKit. I was curious to see what we can build if using only Apple technologies. How many lines of code are needed to implement this useful feature? Each year in WWDC you can notice that Apple engineers update MapKit rigorously adding new features especially if it comes to SwiftUI. I used only SwiftUI building Address with an autocompletion feature with Map because I truly believe that this framework is our closest future and UIKit soon will be secondary technology.

Source Code

GitHub: https://github.com/maxkalik/address-autocomplete-swiftui

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