ReactiveUI OneWayBind泄漏句柄

Question

我有一个简单的ViewModel:

public class MeetingPageViewModel : ReactiveObject, IRoutableViewModel
{
    public MeetingPageViewModel(IScreen hs, IMeetingRef mRef)
    {
        HostScreen = hs;
        _backing = "hi there";
    }

    public IScreen HostScreen { get; private set; }

    public string MeetingTitle
    {
        get { return _backing; }
        set { this.RaiseAndSetIfChanged(ref _backing, value); }
    }
    string _backing;

    public string UrlPathSegment
    {
        get { return "/meeting"; }
    }
}

然后我将一个TextBlock绑定到MeetingTitle:

public sealed partial class MeetingPage : Page, IViewFor<MeetingPageViewModel>
{
    public MeetingPage()
    {
        this.InitializeComponent();

        // Bind everything together we need.
        this.OneWayBind(ViewModel, x => x.MeetingTitle, y => y.MeetingTitle.Text);
    }

    /// <summary>
    /// Stash the view model
    /// </summary>
    public MeetingPageViewModel ViewModel
    {
        get { return (MeetingPageViewModel)GetValue(ViewModelProperty); }
        set { SetValue(ViewModelProperty, value); }
    }
    public static readonly DependencyProperty ViewModelProperty =
        DependencyProperty.Register("ViewModel", typeof(MeetingPageViewModel), typeof(MeetingPage), new PropertyMetadata(null));

    object IViewFor.ViewModel
    {
        get { return ViewModel; }
        set { ViewModel = (MeetingPageViewModel)value; }
    }
}

导航回上一屏幕后,SessionPageViewModel不会被垃圾回收.我正在使用6.4.1的RxUI和VS2013(以及内存分析分析工具).如果我处理OneWayBind的返回值,那么一切都会被正确清理 - 但当然,我不再拥有绑定.

Answer 1

事实证明问题是DependencyProperty ViewModel.它的生命是永恒的(请注意其声明中的"静态").因此,附加到它的绑定永远不会被垃圾收集,因为它永远不会消失,然后绑定会持有对视图和视图模型的引用,因此它们永远不会消失.

打破这种情况的唯一方法是明确清理绑定.RxUI提供了WhenActivated方法来帮助解决这个问题.将绑定包围在lambda中,并使用提供的函数来跟踪IDisposals.当视图消失时,这将被清除.

this.WhenActivated(disposeOfMe => {
    disposeOfMe (this.OneWayBind(ViewModel, x => x.MeetingTitle, y => y.MeetingTitle.Text));
});