NSAutoReleasePool and async functions

I have a function in my program that creates new widgets to represent data, however whenever a widget is created i get alot of "AutoRelease with no NSAutoReleasePool in place" error messages. Since an NSAutoReleasePool should be automatically created on the main thread, I have an inkling that these error messages appear because an async function might create my threads...

This is the function called to create widgets to represent the latest information. This function is called pretty often:

    private void CreateAndDisplayTvShowWidget (TvShow show)
    {
        var Widget = new TvShowWidgetController (show);
        Widget.OnRemoveWidget += ConfirmRemoveTvShow;

        Widget.View.SetFrameOrigin (new PointF (0, -150));
        Widget.View.SetFrameSize (new SizeF (ContentView.Frame.Width, 150));

        ContentView.AddSubview (Widget.View);
        show.ShowWidget = Widget;
    }

This function is usually called when this async function returns:

    private static void WebRequestCallback (IAsyncResult result)
    {
        HttpWebRequest request = (HttpWebRequest)result.AsyncState;
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse (result);

        StreamReader responseStream = new StreamReader (response.GetResponseStream ());
        string responseString = responseStream.ReadToEnd ();
        responseStream.Close ();

        ProcessResponse (responseString, request);
    }

ProcessResponse (responseString, request) looks like this:

    private static void ProcessResponse (string responseString, HttpWebRequest request)
    {
        string requestUrl = request.Address.ToString ();

        if (requestUrl.Contains (ShowSearchTag)) {
            List<TvShow> searchResults = TvDbParser.ParseTvShowSearchResults (responseString);
            TvShowSearchTimeoutClock.Enabled = false;
            OnTvShowSearchComplete (searchResults);
        } else if (requestUrl.Contains (MirrorListTag)) {
            MirrorList = TvDbParser.ParseMirrorList (responseString);
            SendRequestsOnHold ();
        } else if (requestUrl.Contains (TvShowBaseTag)) {
            TvShowBase showBase = TvDbParser.ParseTvShowBase (responseString);
            OnTvShowBaseRecieved (showBase);
        } else if (requestUrl.Contains (ImagePathReqTag)) {
            string showID = GetShowIDFromImagePathRequest (requestUrl);
            TvShowImagePath imagePath = TvDbParser.ParseTvShowImagePath (showID, responseString);
            OnTvShowImagePathRecieved (imagePath);
        }
    }

Cr开发者_运维技巧eateAndDisplayTvShowWidget (TvShow show) is called when the event OnTvShowBaseRecieved (TvShow) is called, which is when I get tons error messages regarding NSAutoReleasePool...

The last two functions are part of what is supposed to be a cross-platform assembly, so I can't have any MonoMac-specific code in there...

I never call any auto-release or release code for my widgets, so I assume that the MonoMac bindings does this automatically as part of its garbage collection?

You can create autorelease pools at point within the call stack, you can even have multiple nested autorelease pools with the same call stack. So you should be able to create your autorelease pools in the async entry functions.

You only need an NSAutoreleasePool if you use the auto-release features of objects. A solution is to create a NSAutoreleasePool around the code that manipulates auto-released objects (in the async callback).

Edit:

Have you tried to encapsulate the creation code with a NSAutoreleasePool ? As this is the only place where you call MonoMac code, this should solve the issue.

private void CreateAndDisplayTvShowWidget (TvShow show)
{
    using(NSAutoreleasePool pool = new NSAutoreleasePool())
    {
        var Widget = new TvShowWidgetController (show);
        Widget.OnRemoveWidget += ConfirmRemoveTvShow;

        Widget.View.SetFrameOrigin (new PointF (0, -150));
        Widget.View.SetFrameSize (new SizeF (ContentView.Frame.Width, 150));

        ContentView.AddSubview (Widget.View);
        show.ShowWidget = Widget;
    }
}

Note that even if you don't use auto-released objects directly, there are some case where the Cococa API use them udner the hood.

I had a similar problem and it was the response.GetResponseStream that was the problem. I surrounded this code with...

using (NSAutoreleasePool pool = new NSAutoreleasePool()) {
}

... and that solved my problem.