Streamlined creation of custom node ports

Instead of initializing port arrays in Init();, ports are now defined by attributes on public fields

Examples/Nodes/BaseNode.cs

@@ -3,6 +3,8 @@
 [System.Serializable]
 public class BaseNode : Node {
 
+    [Input] public string input;
+    [Output] public string output;
     public bool concat;
     [TextArea]
     public string SomeString;
@@ -10,11 +12,4 @@ public class BaseNode : Node {
     public Color col;
     public AnimationCurve anim;
     public Vector3 vec;
-    protected override void Init() {
-        inputs = new NodePort[2];
-        inputs[0] = CreateNodeInput("IntInput", typeof(int));
-        inputs[1] = CreateNodeInput("StringInput", typeof(string));
-        outputs = new NodePort[1];
-        outputs[0] = CreateNodeOutput("StringOutput", typeof(string));
-    }
 }

Examples/Nodes/MathNode.cs

@@ -2,25 +2,11 @@
 
 [System.Serializable]
 public class MathNode : Node {
-
+    [Input] public float a;
+    [Input] public float b;
+    [Output] public float result;
     public enum ValueType { Float, Int }
     public enum MathType { Add, Subtract, Multiply, Divide}
     public ValueType valueType = ValueType.Float;
     public MathType mathType = MathType.Add;
-
-    protected override void Init() {
-        inputs = new NodePort[2];
-        inputs[0] = CreateNodeInput("A", typeof(float));
-        inputs[1] = CreateNodeInput("B", typeof(float));
-        outputs = new NodePort[1];
-        outputs[0] = CreateNodeOutput("Result", typeof(float));
-    }
-
-    public void OnValidate() {
-        System.Type type = typeof(int);
-        if (valueType == ValueType.Float) type = typeof(float);
-        inputs[0].type = type;
-        inputs[1].type = type;
-        outputs[0].type = type;
-    }
 }

Scripts/Editor/NodeEditor.cs

@@ -14,11 +14,11 @@ public class NodeEditor {
     public virtual void OnNodeGUI() {
         portRects.Clear();
         DrawNodePortsGUI();
-        DrawDefaultNodeGUI();
+        DrawDefaultNodeBody();
     }
 
     /// <summary> Draws standard field editors for all public fields </summary>
-    protected void DrawDefaultNodeGUI() {
+    protected void DrawDefaultNodeBody() {
         FieldInfo[] fields = GetInspectorFields(target);
         for (int i = 0; i < fields.Length; i++) {
             Type fieldType = fields[i].FieldType;
@@ -31,6 +31,9 @@ public class NodeEditor {
                 EditorGUILayout.LabelField(headerAttrib.header);
             }
 
+            //Skip if field has input or output attribute
+            if (NodeEditorUtilities.HasAttrib<Node.InputAttribute>(fieldAttribs) || NodeEditorUtilities.HasAttrib<Node.OutputAttribute>(fieldAttribs)) continue;
+
             EditorGUI.BeginChangeCheck();
             if (fieldType == typeof(int)) {
                 fieldValue = EditorGUILayout.IntField(fieldName, (int)fieldValue);

Scripts/Editor/NodeEditorUtilities.cs

@@ -23,6 +23,15 @@ public static class NodeEditorUtilities {
         return false;
     }
 
+    public static bool HasAttrib<T>(object[] attribs) where T : Attribute {
+        for (int i = 0; i < attribs.Length; i++) {
+            if (attribs[i].GetType() == typeof(T)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     /// <summary> Return color based on type </summary>
     public static Color GetTypeColor(Type type) {
         UnityEngine.Random.InitState(type.Name.GetHashCode());

Scripts/Node.cs

@@ -14,18 +14,21 @@ public abstract class Node {
     [SerializeField] private string nodeType;
 
     [SerializeField] public Rect position = new Rect(0,0,200,200);
-    [SerializeField] protected NodePort[] inputs = new NodePort[0];
-    [SerializeField] protected NodePort[] outputs = new NodePort[0];
+    [SerializeField] private NodePort[] inputs = new NodePort[0];
+    [SerializeField] private NodePort[] outputs = new NodePort[0];
 
     public int InputCount { get { return inputs.Length; } }
     public int OutputCount { get { return outputs.Length; } }
 
     protected Node() {
         nodeType = GetType().ToString();
+        CachePorts();
         Init();
     }
 
-    protected abstract void Init();
+    protected virtual void Init() {
+
+    }
 
     public int GetInputId(NodePort input) {
         for (int i = 0; i < inputs.Length; i++) {
@@ -75,4 +78,40 @@ public abstract class Node {
     public override int GetHashCode() {
         return JsonUtility.ToJson(this).GetHashCode();
     }
+
+    [AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
+    public class InputAttribute : Attribute {
+        public InputAttribute() {
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
+    public class OutputAttribute : Attribute {
+        public OutputAttribute() {
+        }
+    }
+
+    /// <summary> Use reflection to find all fields with <see cref="InputAttribute"/> or <see cref="OutputAttribute"/>, and write to <see cref="inputs"/> and <see cref="outputs"/> </summary>
+    private void CachePorts() {
+        List<NodePort> inputPorts = new List<NodePort>();
+        List<NodePort> outputPorts = new List<NodePort>();
+
+        System.Reflection.FieldInfo[] fieldInfo = GetType().GetFields();
+        for (int i = 0; i < fieldInfo.Length; i++) {
+            //Get InputAttribute and OutputAttribute
+            object[] attribs = fieldInfo[i].GetCustomAttributes(false);
+            InputAttribute inputAttrib =  null;
+            OutputAttribute outputAttrib = null;
+            for (int k = 0; k < attribs.Length; k++) {
+                if (attribs[k] is InputAttribute) inputAttrib = attribs[k] as InputAttribute;
+                else if (attribs[k] is OutputAttribute) outputAttrib = attribs[k] as OutputAttribute;
+            }
+            if (inputAttrib != null && outputAttrib != null) Debug.LogError("Field " + fieldInfo + " cannot be both input and output.");
+            else if (inputAttrib != null) inputPorts.Add(new NodePort(fieldInfo[i].Name, fieldInfo[i].FieldType, this, NodePort.IO.Input));
+            else if (outputAttrib != null) outputPorts.Add(new NodePort(fieldInfo[i].Name, fieldInfo[i].FieldType, this, NodePort.IO.Output));
+        }
+
+        inputs = inputPorts.ToArray();
+        outputs = outputPorts.ToArray();
+    }
 }