如何封装可观察的长反应链的创建

Question

目前我有以下 Rx/ReactiveUI 代码块：

        this.WhenAnyValue(x => x.Listras)
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(im => GetArray.FromChannels(im, 0, 1))
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.Grayscale, out _grayscale);

        this.WhenAnyValue(x => x.Grayscale)
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(ar => Gaussian.GaussianConvolution(ar, 1.5))
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.BlurMenor, out _blurMenor);

        this.WhenAnyValue(x => x.BlurMenor)
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.ImagemBlurMenor, out _imagemBlurMenor);

        this.WhenAnyValue(x => x.BlurMenor)
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(ar => Gaussian.VerticalGaussianConvolution(ar, 5))
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.BlurMaior, out _blurMaior);

        this.WhenAnyValue(x => x.BlurMaior)
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.ImagemBlurMaior, out _imagemBlurMaior);

        this.WhenAnyValue(x => x.BlurMenor, x => x.BlurMaior)
            .Where(tuple => tuple.Item1 != null && tuple.Item2 != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(tuple => ArrayOperations.Diferença(tuple.Item1, tuple.Item2))
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.Diferença, out _diferença);

        this.WhenAnyValue(x => x.Diferença)
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(millis))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
            .ObserveOn(RxApp.MainThreadScheduler)
            .ToProperty(this, x => x.ImagemDiferença, out _imagemDiferença);

如您所见，它公然违反了 DRY 原则，但我不知道如何将属性和委托的传递参数化。

在 Rx/ReactiveUI 中自动创建这些方法链的常用方法是什么？

Answer 1

Rx 的美妙之处在于您可以基于其他运算符创建自己的运算符。这是因为 Rx 的功能方面。

您可以创建一个新的运算符来封装所有常见行为，并将细微的差异作为参数：

// Put this class somewhere useful. Either beside your VM inside the same namespace
// Or in a seperate file for all your custom operators
public static class ObservableMixins
{
    public static IObservable<TOut> ThrottledSelect<TIn, TOut>(this IObservable<TIn> source, int milliseconds, Func<TIn, TOut> selector) =>
        source
            .Where(item => item != null)
            .Throttle(TimeSpan.FromMilliseconds(milliseconds))
            .ObserveOn(TaskPoolScheduler.Default)
            .Select(selector)
            .ObserveOn(RxApp.MainThreadScheduler)
}

这样使用它：

this.WhenAnyValue(x => x.Listras)
    .ThrottledSelect(millis, im => GetArray.FromChannels(im, 0, 1))
    .ToProperty(this, x => x.Grayscale, out _grayscale);

this.WhenAnyValue(x => x.Grayscale)
    .ThrottledSelect(millis, ar => Gaussian.GaussianConvolution(ar, 1.5))
    .ToProperty(this, x => x.BlurMenor, out _blurMenor);

this.WhenAnyValue(x => x.BlurMenor)
    .ThrottledSelect(millis, ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
    .ToProperty(this, x => x.ImagemBlurMenor, out _imagemBlurMenor);

this.WhenAnyValue(x => x.BlurMenor)
    .ThrottledSelect(millis, ar => Gaussian.VerticalGaussianConvolution(ar, 5))
    .ToProperty(this, x => x.BlurMaior, out _blurMaior);

this.WhenAnyValue(x => x.BlurMaior)
    .ThrottledSelect(millis, ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
    .ToProperty(this, x => x.ImagemBlurMaior, out _imagemBlurMaior);

this.WhenAnyValue(x => x.BlurMenor, x => x.BlurMaior)
    // Notice how I'm returning a null if either item is null
    // It will be filtered in the operator
    .Select(tuple => tuple.Item1 != null || tuple.Item2 != null ? null : tuple)
    .ThrottledSelect(millis, tuple => ArrayOperations.Diferença(tuple.Item1, tuple.Item2))
    .ToProperty(this, x => x.Diferença, out _diferença);

this.WhenAnyValue(x => x.Diferença)
    .ThrottledSelect(millis, ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
    .ToProperty(this, x => x.ImagemDiferença, out _imagemDiferença);

如果您觉得不那么冒险，您当然可以将其用作常规方法，该方法采用 observable：

public IObservable<T> ThrottledSelect<TIn, TOut>(IObservable<TIn> source, int milliseconds, Func<TIn, TOut> selector) =>
    source
        .Where(item => item != null)
        .Throttle(TimeSpan.FromMilliseconds(milliseconds))
        .ObserveOn(TaskPoolScheduler.Default)
        .Select(selector)
        .ObserveOn(RxApp.MainThreadScheduler)

并像这样使用它：

ThrottledSelect(this.WhenAnyValue(x => x.Diferença), millis, ar => { ConversorImagem.Converter(ar, out BitmapSource im); return im; })
    .ToProperty(this, x => x.ImagemDiferença, out _imagemDiferença);