[MonoTouch] Subscribing to ScrollAnimationEnded on a uitableview has strange results?

[Jason Awbrey]

someone else can probably explain this better, but the general rule is that
you can either assign a delegate to a class, or you can use C# style event
handlers, but you can't do both.  I think in this case you are trying to do
both - the UITableViewSource is a combined datasource/delegate.

I imagine that when you assign a C# event handler, MT is creating a
delegate for you under the covers, which clears out the delegate that you
had manually assigned.

On Tue, Mar 6, 2012 at 6:19 PM, victoria <iminurbase at hotmail.com> wrote:

> Hello list, hope you can shed some light on this odd issue we're having.
>
> Today I helped track down a really obscure bug. What it came down to is
> this: deep in the code an uitableview had its ScrollAnimationEnded
> subscribed to, and when that happened the uitableview.Source for some
> reason
> got set to null.
>
> I think the best way I can explain it is with a simple test case:
>
> ---
>    class DoNothing : UITableViewSource
>    {
>      public override int RowsInSection (UITableView tableview, int section)
> { return 0; }
>      public override UITableViewCell GetCell (UITableView tableView,
> NSIndexPath indexPath)
>      {
>        return new UITableViewCell();
>      }
>    }
>
>    public override void ViewDidLoad ()
>    {
>      UITableView tableview = new UITableView();
>      tableview.Source = new DoNothing();
>
>      Console.WriteLine("source null? " + (tableview.Source == null));  //
> false
>      tableview.ScrollAnimationEnded += (s, e) => { };
>      Console.WriteLine("source null? " + (tableview.Source == null));  //
> true, what happened here?
>    }
> ---
>
> we worked around the problem by saving the uitableview.source just before
> subscribing to the event, then in the event handler we simply set the
> source
> again. This seem to work and luckily we don't really need the source until
> the event has fired, but I can't for my life understand WHY .source is
> cleared on subscribing to the event, or what else happens that we haven't
> noticed yet (hint: this is the real question that worries me).
>
> This by the way, doesn't work either:
>
> var tmp = tableview.Source;
> tableview.ScrollAnimationEnded += (s, e) => { };
> tableview.Source = tmp;
>
> Because setting Source to tmp clears the subscribed event. Is this really
> expected behavior, are we missing something? Or maybe, what is the proper
> way to subscribe to ScrollAnimationEnded without strange side effects?
>
> / V
>
> --
> View this message in context:
> http://monotouch.2284126.n4.nabble.com/Subscribing-to-ScrollAnimationEnded-on-a-uitableview-has-strange-results-tp4451815p4451815.html
> Sent from the MonoTouch mailing list archive at Nabble.com.
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