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Utility to create custom VisualElements that correspond to specific types in Unity
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| using UnityEngine; | |
| using UnityEditor; | |
| using UnityEngine.UIElements; | |
| using System; | |
| using System.Collections.Generic; | |
| public static class ControlUtility | |
| { | |
| private static class ControlCache<TBaseControl, TBaseObject> where TBaseControl : VisualElement where TBaseObject : class | |
| { | |
| // Key is object type, value is control type. | |
| public static readonly Dictionary<Type, Type> cache = new Dictionary<Type, Type>(); | |
| } | |
| public static TBaseControl CreateControl<TBaseControl, TBaseObject>(Type objectType) where TBaseControl : VisualElement where TBaseObject : class | |
| { | |
| var baseObjectType = typeof(TBaseObject); | |
| if (!baseObjectType.IsAssignableFrom(objectType)) | |
| { | |
| Debug.LogError("Object Type is not compatible with Base Object Type"); | |
| return null; | |
| } | |
| var cache = ControlCache<TBaseControl, TBaseObject>.cache; | |
| if (!cache.TryGetValue(objectType, out Type controlType)) | |
| { | |
| var controlTypes = TypeCache.GetTypesDerivedFrom<TBaseControl>(); | |
| controlType = FindControlType(controlTypes, objectType, baseObjectType); | |
| cache[objectType] = controlType; | |
| } | |
| if (controlType == null) | |
| return null; | |
| return Activator.CreateInstance(controlType) as TBaseControl; | |
| } | |
| private static Type FindControlType(IList<Type> controlTypes, Type objectType, Type baseObjectType) | |
| { | |
| for (int i = 0; i < controlTypes.Count; i++) | |
| { | |
| var ct = controlTypes[i]; | |
| // We force a parameterless constructor to ensure that we can create an instance of the control. | |
| if (ct.IsAbstract || ct.GetConstructor(Type.EmptyTypes) == null) | |
| continue; | |
| var attributes = ct.GetCustomAttributes(typeof(CustomControlAttribute), false); | |
| foreach (var a in attributes) | |
| if ((a as CustomControlAttribute).inspectedType == objectType) | |
| return ct; | |
| } | |
| // If we didn't find a control type, we search recursively up the inheritance chain, until reaching the base type. | |
| if (baseObjectType != objectType) | |
| return FindControlType(controlTypes, objectType.BaseType, baseObjectType); | |
| return null; | |
| } | |
| } | |
| [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = true)] | |
| public class CustomControlAttribute : Attribute | |
| { | |
| public Type inspectedType { get; } | |
| public CustomControlAttribute(Type inspectedType) | |
| { | |
| this.inspectedType = inspectedType; | |
| } | |
| } |
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| // Suppose we have a custom base node class and a child node class: | |
| public abstract class NodeBase { } | |
| public class ChildNode : NodeBase { } | |
| //We then can have a base NodeControl to be shown inside some interface for each of its nodes: | |
| [CustomControl(typeof(NodeBase))] | |
| public class NodeControl : VisualElement | |
| { | |
| public abstract void Init(NodeBase node) | |
| { | |
| //Do your thing. | |
| } | |
| } | |
| // The NodeControl will work as a fallback for all node types, but we also want a specific UI for ChildNode: | |
| [CustomControl(typeof(ChildNode))] | |
| public class ChildNodeControl : NodeControl | |
| { | |
| public override void Init(NodeBase node) | |
| { | |
| //Do your thing. | |
| } | |
| } | |
| // Then, to create the appropriate NodeControl for a given node we can do this: | |
| var control = ControlUtility.CreateControl<NodeControl, NodeBase>(myNode.GetType()); | |
| control.Init(myNode); |
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