比如我有
private void test(Action> fn)
{
fn(("hello", 10));
}
test(t =>
{
var (s, i) = t;
Console.WriteLine(s);
Console.WriteLine(i);
});
我想写这样的东西
private void test(Action> fn)
{
fn(("hello", 10));
}
test((s,i) =>
{
Console.WriteLine(s);
Console.WriteLine(i);
});
这有可能用一些正确的表示法吗？
1> Paulo Morgad..：
您可以将其缩短为:
void test( Action> fn)
{
fn(("hello", 10));
}
test(((string s, int i) t) =>
{
Console.WriteLine(t.s);
Console.WriteLine(t.i);
});
希望有一天我们可以将参数从元组映射到方法调用:
void test(Action> fn)
{
fn(@("hello", 10)); // <-- made up syntax
}
test((s, i) =>
{
Console.WriteLine(s);
Console.WriteLine(i);
});
但目前还没有.
fn（@（“ hello”，10））;`没有意义。它仍在向该函数传递一个元组，因此只要`fn（（“ hello”，10））;`就足够了。我们不需要任何特殊的语法，只需要更好的类型推断即可。试想一下最简单的`test（（（（str，inte））=>`），它将表明（str，inte）是单个未命名的元组类型参数。未命名的参数允许将`str`和`inte`视为特殊名称。从传入的元组解构的局部自动变量，与`test（（（（string，int）p）=>`）不同，在这里，parameter是名称，（string，int）是具有字段Item1，Item2的给定类型的非元组。
2> Glenn Slayde..：
I.具有distingle-args与单个n元组参数的Action/ Func委托示例：
// 1. Action with 3 distinct 'int' parameters
Action ArgsAction = (i1, i2, i3) => i1 += i2 += i3;
// 2. Func with 3 distinct 'int' parameters, returning 'long'
Func ArgsFunc = (i1, i2, i3) => (long)i1 + i2 + i3;
// 3. Action with a single 3-tuple parameter
Action<(int, int, int)> TupleAction = args => args.Item1 += args.Item2 += args.Item3;
// 4. Action with a single 3-tuple parameter, returning 'long'
Func<(int, int, int), long> TupleFunc = args => (long)args.Item1 + args.Item2 + args.Item3;
二。演示直接使用上述示例
long r;
// pass distinct params to multi-arg methods
ArgsAction(1, 2, 3); // 1.
r = ArgsFunc(1, 2, 3); // 2.
// pass tuple to tuple-taking methods
TupleAction((1, 2, 3)); // 3.
r = TupleFunc((1, 2, 3)); // 4.
下两节中的示例以其各自的非本地参数形式调用委托。要延迟方法调用或保留适合的委托以进行缓存或延迟/多次调用，请参见VI。和VII。
三，将元组分散（“ splat”）到多参数方法中。
(1, 2, 3).Scatter(ArgsAction); // 1.
r = (1, 2, 3).Scatter(ArgsFunc); // 2.
IV。将不同的args传递给采用元组的方法：
TupleAction.Gather(1, 2, 3); // 3.
r = TupleFunc.Gather(1, 2, 3); // 4.
V.扩展方法Scatter，Gather在上文（III）和（IV）中使用：
// disperse n-tuple into Action arguments
public static void Scatter(in this (T0 i0, T1 i1) t, Action a) => a(t.i0, t.i1);
public static void Scatter(in this (T0 i0, T1 i1, T2 i2) t, Action a) => a(t.i0, t.i1, t.i2);
public static void Scatter(in this (T0 i0, T1 i1, T2 i2, T3 i3) t, Action a) => a(t.i0, t.i1, t.i2, t.i3);
// disperse n-tuple into Func arguments
public static TResult Scatter(in this (T0 i0, T1 i1) t, Func f) => f(t.i0, t.i1);
public static TResult Scatter(in this (T0 i0, T1 i1, T2 i2) t, Func f) => f(t.i0, t.i1, t.i2);
public static TResult Scatter(in this (T0 i0, T1 i1, T2 i2, T3 i3) t, Func f) => f(t.i0, t.i1, t.i2, t.i3);
// accumulate 'n' distinct args and pass into Action as an n-tuple
public static void Gather(this Action<(T0, T1)> a, T0 i0, T1 i1) => a((i0, i1));
public static void Gather(this Action<(T0, T1, T2)> a, T0 i0, T1 i1, T2 i2) => a((i0, i1, i2));
public static void Gather(this Action<(T0, T1, T2, T3)> a, T0 i0, T1 i1, T2 i2, T3 i3) => a((i0, i1, i2, i3));
// accumulate 'n' distinct args and pass into Func as an n-tuple
public static TResult Gather(this Func<(T0, T1), TResult> f, T0 i0, T1 i1) => f((i0, i1));
public static TResult Gather(this Func<(T0, T1, T2), TResult> f, T0 i0, T1 i1, T2 i2) => f((i0, i1, i2));
public static TResult Gather(this Func<(T0, T1, T2, T3), TResult> f, T0 i0, T1 i1, T2 i2, T3 i3) => f((i0, i1, i2, i3));
VI。奖金回合。如果您打算以其备用格式多次调用元组或与众不同的参数的委托，或者还没有准备好实际调用它，则可能希望从元组采用的形式显式地预先转换委托给等效的distingle-args委托，反之亦然。您可以缓存转换后的委托，以供以后多次重复使用。
var ga = ArgsAction.ToGathered(); // 1.
// later...
ga((1, 2, 3));
// ...
ga((4, 5, 6));
var gf = ArgsFunc.ToGathered(); // 2.
// later...
r = gf((1, 2, 3));
// ...
r = gf((4, 5, 6));
var sa = TupleAction.ToScattered(); // 3.
// later...
sa(1, 2, 3);
// ...
sa(4, 5, 6);
var sf = TupleFunc.ToScattered(); // 4.
// later...
r = sf(1, 2, 3);
// ...
r = sf(4, 5, 6);
// of course these approaches also supports in-situ usage:
ArgsAction.ToGathered()((1, 2, 3)); // 1.
r = ArgsFunc.ToGathered()((1, 2, 3)); // 2.
TupleAction.ToScattered()(1, 2, 3); // 3.
r = TupleFunc.ToScattered()(1, 2, 3); // 4.
七。VI中显示的奖金示例的扩展方法。
// convert tuple-taking Action delegate to distinct-args form
public static Action ToScattered(this Action<(T0, T1)> a) => (i0, i1) => a((i0, i1));
public static Action ToScattered(this Action<(T0, T1, T2)> a) => (i0, i1, i2) => a((i0, i1, i2));
public static Action ToScattered(this Action<(T0, T1, T2, T3)> a) => (i0, i1, i2, i3) => a((i0, i1, i2, i3));
// convert tuple-taking Func delegate to its distinct-args form
public static Func ToScattered(this Func<(T0, T1), TResult> f) => (i0, i1) => f((i0, i1));
public static Func ToScattered(this Func<(T0, T1, T2), TResult> f) => (i0, i1, i2) => f((i0, i1, i2));
public static Func ToScattered(this Func<(T0, T1, T2, T3), TResult> f) => (i0, i1, i2, i3) => f((i0, i1, i2, i3));
// convert distinct-args Action delegate to tuple-taking form
public static Action<(T0, T1)> ToGathered(this Action a) => t => a(t.Item1, t.Item2);
public static Action<(T0, T1, T2)> ToGathered(this Action a) => t => a(t.Item1, t.Item2, t.Item3);
public static Action<(T0, T1, T2, T3)> ToGathered(this Action a) => t => a(t.Item1, t.Item2, t.Item3, t.Item4);
// convert distinct-args Func delegate to its tuple-taking form
public static Func<(T0, T1), TResult> ToGathered(this Func f) => t => f(t.Item1, t.Item2);
public static Func<(T0, T1, T2), TResult> ToGathered(this Func f) => t => f(t.Item1, t.Item2, t.Item3);
public static Func<(T0, T1, T2, T3), TResult> ToGathered(this Func f) => t => f(t.Item1, t.Item2, t.Item3, t.Item4);
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