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Rx:忽略订阅服务器导致的更新

system.reactive silverlight-4.0 silverlight c#

Bryan Anderson · 技术社区 · 15 年前

INotifyPropertyChanged 我在追踪 PropertyChanged 两者都有。我想做的是随时运行一个操作 source.PropertyChanged 直到 target.PropertyChanged 是升起的。我可以这样做:

INotifyPropertyChanged source;
INotifyPropertyChanged target;

var sourcePropertyChanged = Observable
    .FromEvent<PropertyChangedEventArgs>(source, "PropertyChanged")
    .Where(x => x.EventArgs.PropertyName == sourcePropertyName);

var targetPropertyChanged = Observable
    .FromEvent<PropertyChangedEventArgs>(target, "PropertyChanged")
    .Where(x => x.EventArgs.PropertyName == targetPropertyName);

sourcePropertyChanged
    .TakeUntil(targetPropertyChanged)
    .ObserveOnDispatcher()
    .Subscribe(_ => /*Raises target.PropertyChanged for targetPropertyName*/);

我现在的问题是我想忽略 财产变更 财产变更 事件由外部源引发。有什么好办法可以做到这一点吗?

3 回复 | 直到 15 年前

Richard Szalay 15 年前

做你所说的事没有固定的方法。这里有一个简单的 SkipWhen

public static IObservable<TSource> SkipWhen(this IObservable<TSource> source, 
    IObservable<TOther> other)
{
    return Observable.Defer<TSource>(() =>
    {
        object lockObject = new object();
        Stack<TOther> skipStack = new Stack<TOther>();

        other.Subscribe(x => { lock(lockObject) { skipStack.Push(x); });

        return source.Where(_ =>
        {
            lock(lockObject);
            {
                if (skipStack.Count > 0)
                {
                    skipStack.Pop();
                    return false;
                }
                else
                {
                    return true;
                }
            }
        });
    });
}

你的代码会像这样更新(见下面的注释):

INotifyPropertyChanged source;
INotifyPropertyChanged target;

// See the link at the bottom of my answer
var sourcePropertyChanged = source.GetPropertyChangeValues(x => x.SourceProperty);

// Unit is Rx's "void"
var targetChangedLocally = new Subject<Unit>();

var targetPropertyChanged = target.GetPropertyChangeValues(x => x.TargetProperty)
    .SkipWhen(targetChangedLocally);

sourcePropertyChanged
    .TakeUntil(targetPropertyChanged)
    .ObserveOnDispatcher()
    .Subscribe(_ =>
    {
        targetChangedLocally.OnNext();
        /*Raises target.PropertyChanged for targetPropertyName*/
    });

注:我最近在博客上提到 a strongly typed IObservable wrapper around INotifyPropertyChanged events

Ronald Wildenberg 15 年前

没有内置的方法,但是您可以使用 Where 可观测的可拓方法。要筛选的条件将是事件的发件人。我想 target.PropertyChanged 事件不同于 PropertyChanged 其他源引发的事件。

Jeffrey van Gogh 15 年前

用这种方法在Rx中使用锁是可以的。锁是短暂的,不会调用用户代码。