gistfile1.cs

using System;

using UIKit;

namespace MemoryTest
{
	public class CustomView : UIView
	{
		public int magicNumber;
	}

	public class CustomButton : UIButton
	{
		public CustomButton() : base(UIButtonType.System)
		{}

		public int someValue;

		~CustomButton()
		{
			Console.WriteLine ("Finalized button");
		}
	}

	public partial class ViewController : UIViewController
	{
		public ViewController (IntPtr handle) : base (handle)
		{
		}

		public override void ViewDidLoad ()
		{
			base.ViewDidLoad ();

			// Test 1: add a subclass of UIView without holding a reference to it.
			//         How is it possible that the unmanaged subview can be cast back to a managed one
			//         and I can access the correct value of magicNumber?
			this.Add(new CustomView { magicNumber = 42 });

			// Test 2: add a subclassed button. This will crash if the button is clicked.
			//         Why would it retain a UIView but not a UIButton?
			var btn = new CustomButton () {
				Frame = new CoreGraphics.CGRect(0, 20, 320, 40),
				someValue = 4711
			};
			btn.SetTitle ("Click me", UIControlState.Normal);
			btn.TouchUpInside += (sender, e) => {
				btn.RemoveFromSuperview();
			};

			this.Add (btn);
		}

		public override void ViewWillAppear (bool animated)
		{
			base.ViewWillAppear (animated);
			GC.Collect ();
			GC.WaitForPendingFinalizers ();
			GC.Collect ();

			var customView = this.View.Subviews [2] as CustomView;
			Console.WriteLine ("Magic number: " + customView.magicNumber);
		}
	}
}