Why is OfflineMapTask failing to generate parameters (Returns "Illegal State")?

[CoryDavis]

I'm working on an iOS app which gets its feature services from an instance of ArcGIS Enterprise.

I'm trying to add the ability to generate an offline map on-demand as described in this article. Currently, the user selects a region of the basemap using a rectangle or polygon and their selection is passed into an OfflineMapTask to generate the parameters, but the completion returns the following error:

"Error Domain=com.esri.arcgis.runtime.error Code=6 "Illegal state" UserInfo={NSLocalizedFailureReason=The online map must have an item property which is its online portal item."

Here is my function. The error branch is always taken, so I edited out the rest of the function to save space.

func takeMapOffline(areaOfInterest: AGSGeometry) {
        //1. Declare offline map task
        let offlineMapTask = AGSOfflineMapTask(onlineMap: self.mapView.map!)
        
        //2. Define parameters
        offlineMapTask.defaultGenerateOfflineMapParameters(withAreaOfInterest: areaOfInterest, completion: {(parameters, error) in
            print("@@@ Generate parameters 1: Start")
            if let error = error {
                print("@@@ Generate parameters 2: Error, getting parameters failed")
                print(error)
                return
            }
            //The success branch here never executes
        })
    }‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Can someone explain what this error means and how I can fix it?

[Nicholas-Furness]

I'd guess you're not creating the AGSMap from a web map (referred to by a portal item) but are rather constructing it using one of the local constructors? You should use initWithItem() or initWithURL().

Does that help?

[CoryDavis]

That's correct, the AGSMap is created using a local constructor. I tried substituting

self.mapView.map = AGSMap.init(url: URL(string: self.mapLayerUrl)!), but I get this error in the completion block of the load method:

"Webmap version is not supported"

I know this is a secondary issue, but can you suggest a workaround for this?

[Nicholas-Furness]

Hmm. When I've seen that, it means the web map is quite old. If you can Save As to create a new copy (or just Save if you're the owner) that should save a version in a recognized web map spec version and should then work.