Async/await location streamer for iOS, watchOS using new concurrency model in Swift

Async pattern using new concurrency model in swift that can be applied to Core Bluetooth, Core Motion and others sources streaming data asynchronously

SwiftUI example of using package

async-location-swift-example

if you are using the simulator don’t forget to simulate locations

Features

• Using new concurrency swift model around CoreLocation manager
• Customizable in terms of CLLocationManager properties
• Streaming current location asynchronously
• Different strategies - Keep and publish all stack of locations since streaming has started or the last one
• Support for iOS from 14.1 and watchOS from 7.0
• Errors handling (as AsyncLocationErrors so CoreLocation errors CLError)

How to use

1. Add to info the option “Privacy - Location When In Use Usage Description”

2. Add or inject LMViewModel into a View

    @EnvironmentObject var model: LMViewModel 

3. Call ViewModel method start() within async environment

If task will be canceled the streaming stops automatically. I would recommend to use .task modifier it manages cancelation on it’s own. If you need to use Task and keep it in @State don’t forget to cancel() when the time has come or it might course memory leaks in some cases

 .task{
       do{
             try await viewModel.start()
         }catch{
             self.error = error.localizedDescription
         }     
    }

4. Bake async stream of data from “locations” into a visual presentation

    @ViewBuilder
    var coordinatesTpl: some View{
        List(viewModel.locations, id: \.hash) { location in
            Text("\(location.coordinate.longitude), \(location.coordinate.latitude)")
        }
    }

5. Showcase error

    ///Access was denied by  user
    case accessIsNotAuthorized
    
    /// Attempt to launch streaming while it's been already started
    /// Subscribe different Views to LMViewModel.locations publisher to feed them
    case streamingProcessHasAlreadyStarted
    
    /// Stream was cancelled
    case streamCanceled

    /// Stream was terminated
    case streamUnknownTermination
    
    /// A Core Location error
    case coreLocationManagerError(CLError)

There’s been a glitch - throwing CLError.locationUnknown Error Domain=kCLErrorDomain Code=0 “(null)” on some devices and simulator while changing locations time by time. This type of error .locationUnknown is excluded when it happens in the delegate method didFailWithError

LMViewModel API

public protocol ILocationManagerViewModel: ObservableObject{
        
    /// List of locations
    @MainActor
    var locations : [CLLocation] { get }
    
    /// Strategy for publishing locations Default value is .keepLast 
    /// .keepAll is an option
    var strategy : LMViewModel.Strategy { get }
    
    /// Start streaming locations
    func start() async throws
    
    /// Stop streaming locations
    func stop()
}

LMViewModel Parameters

Param	Description
strategy	Strategy for publishing locations Default value is .keepLast The other option is .keepAll
accuracy	The accuracy of a geographical coordinate.
activityType	Constants indicating the type of activity associated with location updates.
distanceFilter	A distance in meters from an existing location.
backgroundUpdates	A Boolean value that indicates whether the app receives location updates when running in the background

Default location

1. Product > Scheme > Edit Scheme
2. Click Run .app
3. Option tab
4. Already checked Core Location > select your location
5. Press OK

Available for watchOS

Documentation(API)

• You need to have Xcode 13 installed in order to have access to Documentation Compiler (DocC)
• Go to Product > Build Documentation or ⌃⇧⌘ D