与委托具有多个参数且没有 EventArgs 的事件集成

Question

FromEvent 或 FromEventPattern 方法似乎没有重载，只有在有更多的情况下才会将 IObservable<T> 类型为 TDelegate 的事件转换为不止一个参数而且没有 EventArgs.

例如看来我们无法将以下内容转换为可观察对象。

public event Action<int, int> SomethingHappened;

public event Func<string, int> SomethingElseHappened;

我们要么必须在某处有一个EventArgs，要么有一个TDelegate，其签名中只有一个参数。因此，以下是可转换的，因为它们的隐式委托中有一个 EventArgs。

public event NameChangedHandler NameChanged;
public event EventHandler RollNumberChanged;
public event EventHandler<AgeChangedEventArgs> AgeChanged;


public delegate void NameChangedHandler(
                     object sender, 
                     NameChangedEventArgs e);

而这个也可以转换，因为它的参数中只有一个T。

public event Action<Tuple<string, string>> ClassChanged;

如果遇到这样的事件我该怎么办：

public event Action<T1, T2...> ItHappened;

Answer 1

使用 class 测试仪

public class Tester
{
    public void FireEvent(int i1, int i2, int i3)
    {
        if(ItHappened != null)
            ItHappened(i1, i2, i3);
    }

    public event Action<int, int, int> ItHappened;
}

您可以将此签名 Observable.FromEvent<TDelegate, TEventArgs> (Func<Action<TEventArgs>, TDelegate>, Action<TDelegate>, Action<TDelegate>) 与转换函数一起使用，如下所示：

var t3 = new Tester();
IObservable<Tuple<int, int, int>> observable = Observable.FromEvent<Action<int, int, int>, Tuple<int, int, int>>(
    onNextHandler => (int i1, int i2, int i3) => onNextHandler(Tuple.Create(i1, i2, i3)),
    h => t3.ItHappened += h,
    h => t3.ItHappened -= h);

using (var disposable = observable.Subscribe(t => Console.WriteLine($"{{{t.Item1}, {t.Item2}, {t.Item3}}}")))
{
    t3.FireEvent(1, 2, 3);
}
t3.FireEvent(1, 2, 3);

关于该重载有很好的参考 here。

Answer 2

我必须说我在事件 public event Func<string, int> SomethingElseHappened; 上遇到了困难，但这是一个奇怪的事件，其中事件实际上 returns 一个值。

使用 public event Action<int, int> SomethingHappened;，但是使用 FromEvent 就很容易了。

鉴于此 class：

public class Foo
{
    public event Action<int, int> SomethingHappened;

    public void OnSomethingHappened(int x, int y)
    {
        this.SomethingHappened?.Invoke(x, y);
    }
}

...然后这个代码：

var foo = new Foo();

var fooSomethingHappened =
    Observable
        .FromEvent<Action<int, int>, Tuple<int, int>>(
            a => (x, y) => a(Tuple.Create(x, y)),
            h => foo.SomethingHappened += h,
            h => foo.SomethingHappened -= h);

fooSomethingHappened
    .Subscribe(t =>
        Console.WriteLine("SomethingHappened: {0} & {1}", t.Item1, t.Item2));

foo.OnSomethingHappened(3, 5);

...给我们：

SomethingHappened: 3 & 5

与委托具有多个参数且没有 EventArgs 的事件集成

Integration with event where the delegate has more than one argument and there are no EventArgs

c#

system.reactive