HierarchyViewModel.GetChildrenCount

Parameters

Returns

int The number of direct child nodes of the specified hierarchy node.

Description

Gets the number of child nodes that a hierarchy node has.

The following example displays how many children each collapsed item has in the Hierarchy window. It uses GetChildrenCount to check whether a collapsed item has children before displaying the label. To use this example, save the script in a folder called Assets/Editor/CountWhenCollapsed. Scripts in an Editor folder can use the Hierarchy module API without additional setup. If you save the script outside of an Editor folder, you must enable the Hierarchy built-in module in the Package Manager window, which also adds the module to your Player builds.

using Unity.Hierarchy;
using Unity.Hierarchy.Editor;
using UnityEditor;
using UnityEngine.UIElements;

namespace Unity.HierarchySamples.Editor
{
    class CountWhenCollapsed
    {
        const string k_ChildrenCountUssClassName = "hierarchy-children-count";

        [InitializeOnLoadMethod]
        static void Initialize()
        {
            HierarchyWindow.BindViewItem += OnBindViewItem;
        }

        static void OnBindViewItem(HierarchyWindow window, HierarchyView view, HierarchyViewItem item)
        {
            HierarchyNode node = item.Node;
            int childrenCount = view.ViewModel.GetChildrenCount(node);
            Label label = item.LeftCustomContainer.Q<Label>(className: k_ChildrenCountUssClassName);

            if (childrenCount > 0 && view.ViewModel.DoesNotHaveFlags(node, HierarchyNodeFlags.Expanded))
            {
                if (label == null)
                {
                    label = new Label();
                    label.AddToClassList(k_ChildrenCountUssClassName);
                    item.LeftCustomContainer.Add(label);
                }

                label.text = $"({childrenCount})";
                label.style.display = DisplayStyle.Flex;
            }
            else
            {
                if (label != null)
                    label.style.display = DisplayStyle.None;
            }
        }
    }
}