Async/Await Example: Download Preplanned Offline Map

AsyncAwait.swift

func downloadPreplannedOfflineMap() async throws {
    guard let area = (try await task.getPreplannedMapAreas()).first else { return }
    
    let params = try await task.defaultDownloadPreplannedOfflineMapParameters(with: area)
    
    let job = task.downloadPreplannedOfflineMapJob(
        with: params,
        downloadDirectory: docsURL.appendingPathComponent(Date().ISO8601Format(), isDirectory: true)
    )
    
    let result = try await job.start { status in
        print("Status updated")
    }
    
    offlineMap = result.offlineMap
    
    print("Map has \(result.offlineMap.operationalLayers.count) layers and \(result.offlineMap.tables.count) tables")
}

AsyncAwaitCall.swift

Task {
    do {
        try await self.downloadPreplannedOfflineMap()
    } catch {
        print("Error downloading preplanned offline map: \(error.localizedDescription)")
    }
}

Completion.swift

var downloadJob: AGSDownloadPreplannedOfflineMapJob?

func downloadPreplannedOfflineMap() {
    task.getPreplannedMapAreas { [weak self] areas, error in
        guard let self = self else { return }
        
        if let error = error {
            print("Error getting map areas: \(error.localizedDescription)")
            return
        }
        
        guard let area = areas?.first, let task = self.task else { return }
        
        task.defaultDownloadPreplannedOfflineMapParameters(with: area) { [weak self] params, error in
            guard let self = self else { return }
            
            if let error = error {
                print("Error getting preplanned map parameters: \(error.localizedDescription)")
                return
            }
            
            guard let params = params else { return }

            let job = task.downloadPreplannedOfflineMapJob(
                with: params,
                downloadDirectory: self.docsURL.appendingPathComponent(Date().ISO8601Format(), isDirectory: true))
            
            self.downloadJob = job
            
            job.start { status in
                print("Status updated")
            } completion: { result, error in
                if let error = error {
                    print("Error downloading preplanned map: \(error.localizedDescription)")
                    return
                }
                
                guard let result = result else {
                    preconditionFailure("No error and no map result!")
                }
                
                self.offlineMap = result.offlineMap
                
                print("Map has \(result.offlineMap.operationalLayers.count) layers and \(result.offlineMap.tables.count) tables")
            }

        }
    }
}

This is an example of interrogating a web map to get its preplanned offline map areas and download the first one. Working with Swift Concurrency makes the code so much more palatable (see arcgis-runtime-ios-async-await).

See also https://developers.arcgis.com/ios/offline-maps-scenes-and-data/download-an-offline-map-preplanned/