Resolved Structs as itemsSource?

Hi here!

Very simple code sample, I have a struct that contains some info for a listView's items. I can add items from script and that works (see line 17).
But if add a new item through the '+' footer icon (listview.showAddRemoveFooter = true) then I get an exception.
Now, exactly same code, I change the struct for a string (so items = new List<string>) then the footer's add works without errors.
The code:

Code (CSharp):

1.  
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UIElements;
5.  
6. public struct stringBool
7. {
8.    public string text;
9.    public bool value;
10. }
11.  
12. public class SampleListView : MonoBehaviour
13. {
14.    public List<stringBool> items = new List<stringBool>();
15.    public void Start()
16.    {
17.        items.Add(new stringBool {text = "lalal"});
18.        var rootVisualElement = GetComponent<UIDocument>().rootVisualElement;
19.        var listView = rootVisualElement.Q<ListView>();
20.        var listItem = Resources.Load<VisualTreeAsset>("SampleListView");
21.  
22.        listView.itemsSource = items;
23.        listView.makeItem = () =>
24.        {
25.            return listItem.Instantiate();
26.        };
27.        listView.bindItem = (e, i) =>
28.        {
29.            e.Q<Label>().text = items[i].text;
30.            e.Q<Button>().text = "Button " + items[i].text;
31.            e.Q<RadioButton>().value = items[i].value;
32.        };
33.    }
34. }
35.  

...and the last lines of the error callstack:

ArgumentNullException: Value cannot be null.

Parameter name: item

System.Collections.Generic.List`1[T].System.Collections.IList.Add (System.Object item) (at <1fe4b731108247d3a7e57fad336611b9>:0)

UnityEngine.UIElements.ListViewController.AddItems (System.Int32 itemCount) (at /Users/bokken/buildslave/unity/build/ModuleOverrides/com.unity.ui/Core/Collections/Controllers/ListViewController.cs:66)

UnityEngine.UIElements.ListView.AddItems (System.Int32 itemCount) (at /Users/bokken/buildslave/unity/build/ModuleOverrides/com.unity.ui/Core/Controls/ListView.cs:383)

UnityEngine.UIElements.ListView.OnAddClicked () (at /Users/bokken/buildslave/unity/build/ModuleOverrides/com.unity.ui/Core/Controls/ListView.cs:447)

Help?

 

Some more info... if I use a class instead of a struct it works... better? I don't get an internal error in Unity but I do get the

listView.bindItem = (e, i) =>

call above being called with a items.count = 1 **but** a items[0] equals to (null). :|

 

So yeah... in case this helps anybody...

This works:

Code (CSharp):

1.  
2. public class SampleListView : MonoBehaviour
3. {
4.    public class stringBool
5.    {
6.        public string text;
7.        public bool value;
8.    }
9.  
10.    List<stringBool> items = new List<stringBool>();
11.    public void Start()
12.    {
13.        var rootVisualElement = GetComponent<UIDocument>().rootVisualElement;
14.        var listView = rootVisualElement.Q<ListView>();
15.        var listItem = Resources.Load<VisualTreeAsset>("SampleListView");
16.  
17.        listView.itemsSource = items;
18.        listView.makeItem = () =>
19.        {
20.            return listItem.Instantiate();
21.        };
22.        listView.bindItem = (e, i) =>
23.        {
24.            items[i] = (items[i] is null)? new stringBool() : items[i];
25.            e.Q<Label>().text = items[i].text;              
26.            e.Q<Button>().text = "Button " + items[i].text;
27.            e.Q<RadioButton>().value = items[i].value;
28.        };
29.    }
30. }
31.  

A couple of things from there:

• If the source is a list of structs it won't work at all and it'll throw an internal error (maybe constrain it to nullable types?)
• I would imagine the entry created by the footer would be newed BEFORE the bind, but that's not the case

But anyway, all good, forward we go!