[英]Rx: Create observable without subject
抱歉,标题太简单了,但我不知道该标题还有什么。
我对Rx相当陌生,并尝试解决以下情况。
物品来自服务器并带有一组供应商。 这些供应商之一将被提名为主要供应商。 为了使它们在WPF中可编辑/可绑定,我创建了一些代理反应式对象,这些对象将对UI中的更改进行“反应”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,我实现了以下代码-该代码使用一个主题来完成工作。
我已经读过主题可能是代码的味道,我想知道我所做的是“正确的方法”还是可以采用一种更清洁的方法。
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.
}
}
尽管看起来不错,但我无法真正进行测试。 至于清洁工,这在情人眼中有点。 对我来说,它似乎更具反应性。
我删除从主题ItemProxy
从“回调”行动VendorProxy
。 ReactiveCommands
是可观察的,并且ReactiveList
可以变成可观察的,因此所有这些都是可在ItemProxy
构造函数中primaryStream
(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.
}
}
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