Rx：创建没有主题的可观察对象

Question

对不起，这个标题太简单了，但我不知道还能用什么标题。

我是 Rx 的新手，我正在尝试解决以下情况。

物品来自 collection 供应商的服务器。其中一个供应商将被提名为主要供应商。为了在 WPF 中使它们 editable/bindable 我创建了一些代理反应 objects 将 "react" 更改 UI 并重新计算一些数字。

为了确保只有一个供应商可以成为主要供应商，我实施了以下代码 - 它使用主题来完成工作。

我读过主题 can be a code smell 我想知道我所做的是否 "the right way" 或者是否有更简洁的方法那可以采取。

public class VendorDto
{
    public string Name { get; set; }
    public bool IsPrimary { get; set; }
}

public class VendorProxy : ReactiveObject
{
    // INPC for Name and other properties. 

    public bool IsPrimary => _isPrimary.Value;
    private readonly ObservableAsPropertyHelper<bool> _isPrimary;

    public ReactiveCommand<Unit, Unit> MakePrimary { get; }

    public VendorProxy(VendorDto dto, IObservable<VendorProxy> primaryVendors, Action<VendorProxy> makePrimary)
    {
        primaryVendors
            .DistinctUntilChanged()
            .Select(x => x == this)
            .ToProperty(this, x => x.IsPrimary, out _isPrimary);

        MakePrimary = ReactiveCommand.Create(() => makePrimary(this), 
            canExecute: this.WhenAnyValue(x => x.IsPrimary, alreadyPrimary => !alreadyPrimary));

        if (dto.IsPrimary) 
            makePrimary(this); // set the initial value of IsPrimary. 
    }

    // implements IEquality.
}

public class ItemProxy : ReactiveObject
{
    private ISubject<VendorProxy> PrimaryVendorSubject { get; } = new BehaviorSubject<VendorProxy>(null);

    public IObservable<VendorProxy> PrimaryVendorChanged => PrimaryVendorSubject;

    public ReactiveList<VendorProxy> Vendors { get; }

    public VendorProxy PrimaryVendor => _primaryVendor.Value;
    private readonly ObservableAsPropertyHelper<VendorProxy> _primaryVendor;

    public Item()
    {
        // these come from a web service.
        var dtos = new[] {
            new Vendor {Name = "Vendor A", IsPrimary = true}, 
            new Vendor {Name = "Vendor B", IsPrimary = false}
        }

        Vendors = new ReactiveList<VendorProxy>(dtos.Select(dto => 
            new VendorProxy(dto, PrimaryVendorChanged, PrimaryVendorSubject.OnNext)));

        // some other subscriptions that require the primary vendor to do their work. 
    }
}

Answer 1

虽然看起来不错，但我无法真正测试它。至于清洁工，那就有点见仁见智了。对我来说，它看起来更具反应性。

我从 ItemProxy 中删除了主题，从 VendorProxy 中删除了 'callback' 操作。 ReactiveCommands 是可观察的，ReactiveList 可以变成可观察的，所以所有这些都可以在 ItemProxy 构造函数中派生（在 primaryStream 变量中）。

public class VendorProxy : ReactiveObject
{
    // INPC for Name and other properties. 

    public bool IsPrimary => _isPrimary.Value;
    private readonly ObservableAsPropertyHelper<bool> _isPrimary;

    public ReactiveCommand<Unit, Unit> MakePrimary => ReactiveCommand.Create(() => Unit.Default, 
        canExecute: this.WhenAnyValue(x => x.IsPrimary, alreadyPrimary => !alreadyPrimary));

    public VendorProxy(VendorDto dto, IObservable<VendorProxy> primaryVendors)
    {
        primaryVendors
            .DistinctUntilChanged()
            .Select(x => x == this)
            .ToProperty(this, x => x.IsPrimary, out _isPrimary);

        if(dto.IsPrimary)
            MakePrimary.Execute();
    }

    // implements IEquality.
}

public class ItemProxy : ReactiveObject
{
    public ReactiveList<VendorProxy> Vendors { get; }

    public VendorProxy PrimaryVendor => _primaryVendor.Value;
    private readonly ObservableAsPropertyHelper<VendorProxy> _primaryVendor;

    public ItemProxy()
    {
        // these come from a web service.
        var dtos = new[] {
            new VendorDto {Name = "Vendor A", IsPrimary = true},
            new VendorDto {Name = "Vendor B", IsPrimary = false}
        };

        Vendors = new ReactiveList<VendorProxy>();

        var primaryStream = Vendors.ItemsAdded.Select(_ => Unit.Default)
            .Merge(Vendors.ItemsRemoved.Select(_ => Unit.Default))
            .Select(_ => Observable.Merge(Vendors.Select(v => v.MakePrimary.Select(__ => v))))
            .Switch();

        primaryStream
            .DistinctUntilChanged()
            .ToProperty(this, x => x.PrimaryVendor, out _primaryVendor);

        var proxies = dtos
            .Select(dto => new VendorProxy(dto, primaryStream));

        Vendors.AddRange(proxies);

        // some other subscriptions that require the primary vendor to do their work. 
    }
}

Rx：创建没有主题的可观察对象

Rx: Create observable without subject

c#

wpf

reactive-programming

system.reactive

reactiveui