Automatically reference components on same object, child, or parent

Hi all,

I am working with Unity for so many years now and I love optimizing workflows. It always bothered me that referencing components is either very manual (with public/serialized fields) , lots of boilerplate (with lazy properties) or inefficient (with GetComponent calls at runtime). Currently, I have lots of references to scripts on the same object or on a child. I wrote a small utility attribute that streamlines this.

Code (CSharp):

1. public class CustomMonoBehaviour : MonoBehaviour
2. {
3.     [ComponentReference(true, false)] public ComponentType _component;
4. }

The property drawer will call GetComponent to retrieve the object of the appropriate type. It has two optional bool parameters to search in children and/or parent game objects. Of course this has a limited use case, but I like it, so I figured I share it. Use it/share it as you please.

Code (CSharp):

1. public class ComponentReferenceAttribute : PropertyAttribute
2. {
3.     // ReSharper disable twice UnusedParameter.Local
4.     public ComponentReferenceAttribute(bool findInChildren = false, bool findInParent = false)
5.     { }
6. }

Code (CSharp):

1. [CustomPropertyDrawer(typeof(ComponentReferenceAttribute))]
2. public class ComponentReferenceDrawer : PropertyDrawer
3. {
4.     public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
5.     {
6.         CustomAttributeData customAttributeData = fieldInfo.CustomAttributes
7.             .FirstOrDefault(a => a.AttributeType == typeof(ComponentReferenceAttribute));
8.         if (customAttributeData == null)
9.         {
10.             EditorGUI.HelpBox(position, "Missing attribute data", MessageType.Warning);
11.             return;
12.         }
13.  
14.         var targetObject = property.serializedObject.targetObject as Component;
15.         if (targetObject == null)
16.         {
17.             EditorGUI.HelpBox(position, "Invalid serialized object", MessageType.Warning);
18.             return;
19.         }
20.  
21.         var searchInChildren = (bool) customAttributeData.ConstructorArguments[0].Value;
22.         var searchInParent = (bool) customAttributeData.ConstructorArguments[1].Value;
23.  
24.         var component = property.objectReferenceValue as Component;
25.         if (component == null) component = targetObject.GetComponent(fieldInfo.FieldType);
26.         if (component == null && searchInChildren)
27.             component = targetObject.GetComponentInChildren(fieldInfo.FieldType);
28.         if (component == null && searchInParent)
29.             component = targetObject.GetComponentInParent(fieldInfo.FieldType);
30.  
31.         if (component != null)
32.         {
33.             property.objectReferenceValue = component;
34.             bool wasEnabled = GUI.enabled;
35.             GUI.enabled = false;
36.             EditorGUI.PropertyField(position, property, label, true);
37.             GUI.enabled = wasEnabled;
38.         }
39.         else
40.             EditorGUI.HelpBox(position, $"Missing {fieldInfo.FieldType}", MessageType.Warning);
41.     }
42. }

 

I wish Unity would add this to their engine by default. This is really great.

 

I got the code working here is the updated code:

/Assets/Code/ComponentReferenceAttribute.cs

Code (CSharp):

1. using UnityEngine;
2.  
3. public class ComponentReferenceAttribute : PropertyAttribute
4. {
5.     // ReSharper disable twice UnusedParameter.Local
6.     public ComponentReferenceAttribute(bool findInChildren = false, bool findInParent = false)
7.     { }
8. }

/Assets/Code/Editor/ComponentReferenceDrawer.cs

Code (CSharp):

1. using System.Collections.Generic;
2. using System.Reflection;
3. using UnityEngine;
4. using UnityEditor;
5.  
6.  
7. [CustomPropertyDrawer(typeof(ComponentReferenceAttribute))]
8. public class ComponentReferenceDrawer : PropertyDrawer
9. {
10.     public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
11.     {
12.         IList<CustomAttributeData> customAttributesData = fieldInfo.GetCustomAttributesData();
13.  
14.         CustomAttributeData customAttributeData = null;
15.  
16.         for(int i = 0; i < customAttributesData.Count; i++)
17.         {
18.             if (customAttributesData[i].AttributeType == typeof(ComponentReferenceAttribute))
19.             {
20.                 customAttributeData = customAttributesData[i];
21.                 break;
22.             }
23.         }
24.  
25.         // .FirstOrDefault(a => a.AttributeType == typeof(ComponentReferenceAttribute));
26.         if (customAttributeData == null)
27.         {
28.             EditorGUI.HelpBox(position, "Missing attribute data", MessageType.Warning);
29.             return;
30.         }
31.  
32.         var targetObject = property.serializedObject.targetObject as Component;
33.         if (targetObject == null)
34.         {
35.             EditorGUI.HelpBox(position, "Invalid serialized object", MessageType.Warning);
36.             return;
37.         }
38.  
39.         var searchInChildren = (bool)customAttributeData.ConstructorArguments[0].Value;
40.         var searchInParent = (bool)customAttributeData.ConstructorArguments[1].Value;
41.  
42.         var component = property.objectReferenceValue as Component;
43.         if (component == null) component = targetObject.GetComponent(fieldInfo.FieldType);
44.         if (component == null && searchInChildren)
45.             component = targetObject.GetComponentInChildren(fieldInfo.FieldType);
46.         if (component == null && searchInParent)
47.             component = targetObject.GetComponentInParent(fieldInfo.FieldType);
48.  
49.         if (component != null)
50.         {
51.             property.objectReferenceValue = component;
52.             bool wasEnabled = GUI.enabled;
53.             GUI.enabled = false;
54.             EditorGUI.PropertyField(position, property, label, true);
55.             GUI.enabled = wasEnabled;
56.         }
57.         else
58.             EditorGUI.HelpBox(position, $"Missing {fieldInfo.FieldType}", MessageType.Warning);
59.     }
60. }

Here is how would use the code:
/Assets/Code/Chunk.cs

Code (CSharp):

1. using UnityEngine;
2.  
3. [RequireComponent(typeof(MeshRenderer))]
4. [RequireComponent(typeof(MeshFilter))]
5. public class Chunk : MonoBehaviour
6. {
7.     [ComponentReference] public MeshRenderer meshRenderer;
8.     [ComponentReference] public MeshFilter meshFilter;
9.  
10.     void Start()
11.     {
12.      
13.     }
14. }
15.  

 

It seems the code wasn't working for you, because you were missing the

using System.Linq; 

statement. Nothing wrong with your solution, though. But Linq is a really useful library that's totally worth checking out