memory-analyzers

A set of Roslyn C# code analyzers for finding memory leaks in iOS and MacCatalyst applications -- with potentially other ideas in the future.

For more information on the "circular reference" problem on Apple platforms, see:

• https://github.com/dotnet/maui/wiki/Memory-Leaks#circular-references-on-ios-and-catalyst

Note that this "circular reference" situation would occur in Swift or Objective-C, so it is not a .NET-specific problem. It does not occur on Android or Windows platforms.

MA0001

Don't define public events in NSObject subclasses:

public class MyView : UIView
{
    // NOPE!
    public event EventHandler MyEvent;
}

MA0002

Don't declare members in NSObject subclasses unless they are:

• WeakReference or WeakReference<T>
• Value types

class MyView : UIView
{
    // NOPE!
    public UIView? Parent { get; set; }

    public void Add(MyView subview)
    {
        subview.Parent = this;
        AddSubview(subview);
    }
}

MA0003

Don't subscribe to events inside NSObject subclasses unless:

• It's your event via this.MyEvent or from a base type.
• The method is static.

class MyView : UIView
{
    public MyView()
    {
        var picker = new UIDatePicker();
        AddSubview(picker);
        picker.ValueChanged += OnValueChanged;
    }
    
    void OnValueChanged(object sender, EventArgs e) { }

    // Use this instead and it doesn't leak!
    //static void OnValueChanged(object sender, EventArgs e) { }
}