c# - 如何在 C# 中组合委托(delegate)

Question

我想实现一个方法，该方法采用两个 Action A1 和 Action A2 委托(delegate)并返回新的委托(delegate)，将它们组合在一起。该方法的签名如下:

public static Action<Tuple<T1,T2>> CombineWith<T1,T2>(this Action<T1> a1, Action<T2> a2)

所以，与其说

{
 A1(t1);
 A2(t2);
}

我希望能够写:

{
A1.CombineWith(A2)(Tuple.Create(t1,t2));
}

这个方法的可能实现是什么？

Answer 1

我想你想要:

public static Action<Tuple<T1,T2>> CombineWith<T1,T2>
            (this Action<T1> action1, Action<T2> action2)
{
    //null-checks here.

    return tuple => {
                       action1(tuple.Item1);
                       action2(tuple.Item2);
                    };
}

用法:

Action<int> a1 = x => Console.Write(x + 1);
Action<string> a2 = x => Console.Write(" " + x + " a week");

var combined = a1.CombineWith(a2);

// output: 8 days a week
combined(Tuple.Create(7, "days"));

---

编辑:顺便说一下，我注意到您在评论中提到“单独讨论会更可取”。在这种情况下，您可以:

public static Action<T1, T2> CombineWith<T1, T2>
            (this Action<T1> action1, Action<T2> action2)
{
    //null-checks here.

    return (x, y) => { action1(x); action2(y); };
}