From 51223864a6799cdb8ff38f6e9ac73a4b1215f6fd Mon Sep 17 00:00:00 2001
From: Hubert Mattusch <mattusch.hubert@gmail.com>
Date: Tue, 13 Sep 2022 22:41:19 +0200
Subject: [PATCH] Add RequireInterface attribute

---
 RequireInterface.meta                         |  8 ++++
 RequireInterface/Editor.meta                  |  8 ++++
 .../Editor/RequireInterfaceDrawer.cs          | 41 +++++++++++++++++++
 .../Editor/RequireInterfaceDrawer.cs.meta     | 11 +++++
 .../RequireInterfaceAttribute.cs              |  0
 .../RequireInterfaceAttribute.cs.meta         | 11 +++++
 6 files changed, 79 insertions(+)
 create mode 100644 RequireInterface.meta
 create mode 100644 RequireInterface/Editor.meta
 create mode 100644 RequireInterface/Editor/RequireInterfaceDrawer.cs
 create mode 100644 RequireInterface/Editor/RequireInterfaceDrawer.cs.meta
 rename RequireInterfaceAttribute.cs => RequireInterface/RequireInterfaceAttribute.cs (100%)
 create mode 100644 RequireInterface/RequireInterfaceAttribute.cs.meta

diff --git a/RequireInterface.meta b/RequireInterface.meta
new file mode 100644
index 0000000..f1a1fa6
--- /dev/null
+++ b/RequireInterface.meta
@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: da80835a1611a5e4d908f51f09e8d3bc
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/RequireInterface/Editor.meta b/RequireInterface/Editor.meta
new file mode 100644
index 0000000..89239d9
--- /dev/null
+++ b/RequireInterface/Editor.meta
@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: 849242dbc213969488426f85222a43a9
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/RequireInterface/Editor/RequireInterfaceDrawer.cs b/RequireInterface/Editor/RequireInterfaceDrawer.cs
new file mode 100644
index 0000000..dfdd4f2
--- /dev/null
+++ b/RequireInterface/Editor/RequireInterfaceDrawer.cs
@@ -0,0 +1,41 @@
+using UnityEngine;
+using UnityEditor;
+/// <summary>
+/// Drawer for the RequireInterface attribute.
+/// </summary>
+[CustomPropertyDrawer(typeof(RequireInterfaceAttribute))]
+public class RequireInterfaceDrawer : PropertyDrawer
+{
+    /// <summary>
+    /// Overrides GUI drawing for the attribute.
+    /// </summary>
+    /// <param name="position">Position.</param>
+    /// <param name="property">Property.</param>
+    /// <param name="label">Label.</param>
+    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+    {
+        // Check if this is reference type property.
+        if (property.propertyType == SerializedPropertyType.ObjectReference)
+        {
+            // Get attribute parameters.
+            var requiredAttribute = this.attribute as RequireInterfaceAttribute;
+            // Begin drawing property field.
+            EditorGUI.BeginProperty(position, label, property);
+            // Draw property field.
+            property.objectReferenceValue = EditorGUI.ObjectField(position, label, property.objectReferenceValue, requiredAttribute.requiredType, true);
+            // Finish drawing property field.
+            EditorGUI.EndProperty();
+        }
+        else
+        {
+            // If field is not reference, show error message.
+            // Save previous color and change GUI to red.
+            var previousColor = GUI.color;
+            GUI.color = Color.red;
+            // Display label with error message.
+            EditorGUI.LabelField(position, label, new GUIContent("Property is not a reference type"));
+            // Revert color change.
+            GUI.color = previousColor;
+        }
+    }
+}
\ No newline at end of file
diff --git a/RequireInterface/Editor/RequireInterfaceDrawer.cs.meta b/RequireInterface/Editor/RequireInterfaceDrawer.cs.meta
new file mode 100644
index 0000000..9c4855e
--- /dev/null
+++ b/RequireInterface/Editor/RequireInterfaceDrawer.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: b430a75a32f8e534f8661d364d842691
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/RequireInterfaceAttribute.cs b/RequireInterface/RequireInterfaceAttribute.cs
similarity index 100%
rename from RequireInterfaceAttribute.cs
rename to RequireInterface/RequireInterfaceAttribute.cs
diff --git a/RequireInterface/RequireInterfaceAttribute.cs.meta b/RequireInterface/RequireInterfaceAttribute.cs.meta
new file mode 100644
index 0000000..868885f
--- /dev/null
+++ b/RequireInterface/RequireInterfaceAttribute.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 29f2a6e637914fe4292225071a7c5157
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: