C#•3w ago

IEnumerable, changes to contained class not applied

Hey, So I have this small code:

private class SlotAmmo
{
    public int SpaceLeft { set; get; }
    public EquipementSlot Slot { set; get; }
}

var slots = Equipements.Select(x => new SlotAmmo()
{
    SpaceLeft = x.Info.MaxHold,
    Slot = x
});
foreach (var s in slots) s.SpaceLeft = 0;
foreach (var s in slots) UnityEngine.Debug.Log($"Value: {s.SpaceLeft}");

private class SlotAmmo
{
    public int SpaceLeft { set; get; }
    public EquipementSlot Slot { set; get; }
}

var slots = Equipements.Select(x => new SlotAmmo()
{
    SpaceLeft = x.Info.MaxHold,
    Slot = x
});
foreach (var s in slots) s.SpaceLeft = 0;
foreach (var s in slots) UnityEngine.Debug.Log($"Value: {s.SpaceLeft}");

Where basically I'm just creating data, setting some values to 0 and then printing them But all my prints show me non-zero values Am I missing something obvious?

9 Replies

ero•3w ago

the problem you're seeing here is related to multiple enumeration. while foreach (var s in slots) s.SpaceLeft = 0; does set the value accordingly, you are then re-enumerating the return value of the Select, which will, once again, set the values back to what you specified in the Select it's a bit of a doozie if you don't know how IEnumerables work

ZirkOP•3w ago

Hmm I was thinking it would been applied since info were stored inside class Should I just do a ToArray to stop it from going back to it then?

ero•3w ago

yes, a ToArray call would solve this, for example maybe this helps visualize it a little bit

MODiX•3w ago

ero

sharplab.io (click here)

int[] space = [123];
var slots = CustomSelect(space, x => new Slot { Value = x ...
foreach (var s in slots)
    Console.WriteLine(s.Value);
foreach (var s in slots)
    s.Value = 0;
foreach (var s in slots)
    Console.WriteLine(s.Value);
IEnumerable<TOther> CustomSelect<T, TOther>(IEnumerable<T>... {
    Console.WriteLine("Enumerating!");
// 10 more lines. Follow the link to view.

int[] space = [123];
var slots = CustomSelect(space, x => new Slot { Value = x ...
foreach (var s in slots)
    Console.WriteLine(s.Value);
foreach (var s in slots)
    s.Value = 0;
foreach (var s in slots)
    Console.WriteLine(s.Value);
IEnumerable<TOther> CustomSelect<T, TOther>(IEnumerable<T>... {
    Console.WriteLine("Enumerating!");
// 10 more lines. Follow the link to view.

React with ❌ to remove this embed.

ZirkOP•3w ago

Amazing, thanks a lot

ero•3w ago

$close

MODiX•3w ago

If you have no further questions, please use /close to mark the forum thread as answered

qqdev•3w ago

@Zirk Rider would also spit out a warning here VS maybe too. What are you using?

ZirkOP•3w ago

I was using VS

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IEnumerable, changes to contained class not applied