Feature Request: Array destructuring

[Meir017]

I would like to be able to destruct an array into multiple objects similar to js's feature

var array = [1,2,3];
var [ b, c, d] = array;
// b = 1, c = 2, d = 3

The syntax could be similar to tuple destructuring:

int[] array = { 1, 2, 3 };

int [ a, b, c] = array;
// or
[int a, int b, int c] = array;
// or
var [ a, b, c] = array;

[stepanbenes]

I think it is already possible in C#7 to use tuple destructuring syntax applied on array by using user-defined extension method Deconstruct.

[HaloFour]

public static class ArrayDestructuringExtensions {
    public static void Deconstruct<T>(this T[] array, out T item1, out T item2, out T item3) {
        item1 = default(T);
        item2 = default(T);
        item3 = default(T);
        if (array != null) {
            if (array.Length > 2) {
                item3 = array[2];
            }
            if (array.Length > 1) {
                item3 = array[1];
            }
            if (array.Length > 0) {
                item3 = array[0];
            }
        }
    }
}

What's kludgy in C# 7.0 is that deconstruction is guaranteed to succeed, so if you try to deconstruct an array that is too small your options are to throw or to succeed with some default value (I chose the latter above). With conditional patterns you should have more options.

Oh, and you'd need an overload per arity. Here's hoping for array patterns.

[jnm2]

Why did you close this? I don't think there's a good solution yet and I've already been in situations where I could use one.

[Meir017]

#388 (comment) is the solution

[jnm2]

@HaloFour included the deficiencies of the approach in the same comment.

[aluanhaddad]

What's kludgy in C# 7.0 is that deconstruction is guaranteed to succeed, so if you try to deconstruct an array that is too small your options are to throw or to succeed with some default value (I chose the latter above). With conditional patterns you should have more options.

How did this happen? This needs fixing. Deconstruction is almost an absurd feature without conditionality.

[HaloFour]

@aluanhaddad

That would be #45. Conditional deconstruction would be a part of the wider feature of pattern matching which was deferred for more bake time.

[riddlemd]

Would love to see this moved forward a bit... seems silly it died on the vine in 2017...

[sgtrusty]

As a (mostly but newly) JavaScript developer, I would like to use this when using C#. Thanks 😊.

[333fred]

This could be done as an extension to #3435. Specifically, it would be filling in this chart: #3107.

[GF-Huang]

We need something like this:

var (host, port) = "github.com:443".Split(':');

[Tobberoth]

For anyone showing up later, this was implemented in C# 11 and huoyaoyuan got the syntax correct.

[333fred]

Yes. At the time, we were still hoping to be able to use the curly braces, but we switched to square brackets later.

[jeremysimmons]

For anyone showing up later, this was implemented in C# 11 and huoyaoyuan got the syntax correct.

@Tobberoth link?

[CyrusNajmabadi]

@jeremysimmons

if ("github.com:443".Split(':') is [var host, var port])

[GF-Huang]

@jeremysimmons

if ("github.com:443".Split(':') is [var host, var port])

Is this supports in .NET 7?