added port setting

Example/ExampleNodeGraph.asset

@@ -12,9 +12,64 @@ MonoBehaviour:
   m_Name: ExampleNodeGraph
   m_EditorClassIdentifier: 
   nodes:
-  - {fileID: 114729867621534192}
   - {fileID: 114708853913061688}
   - {fileID: 114511978881715272}
+  - {fileID: 114509033286994848}
+  - {fileID: 114245496101350052}
+--- !u!114 &114245496101350052
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_PrefabParentObject: {fileID: 0}
+  m_PrefabInternal: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 98f6f901f0da53142b79277ea3f42518, type: 3}
+  m_Name: DisplayValue
+  m_EditorClassIdentifier: 
+  graph: {fileID: 11400000}
+  position: {x: -168, y: 8}
+  ports:
+    keys:
+    - input
+    values:
+    - _fieldName: input
+      _node: {fileID: 114245496101350052}
+      _typeQualifiedName: System.Object, mscorlib, Version=2.0.0.0, Culture=neutral,
+        PublicKeyToken=b77a5c561934e089
+      connections:
+      - fieldName: result
+        node: {fileID: 114511978881715272}
+      _direction: 0
+      _connectionType: 1
+      _dynamic: 1
+--- !u!114 &114509033286994848
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_PrefabParentObject: {fileID: 0}
+  m_PrefabInternal: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 98f6f901f0da53142b79277ea3f42518, type: 3}
+  m_Name: DisplayValue
+  m_EditorClassIdentifier: 
+  graph: {fileID: 11400000}
+  position: {x: 72, y: -72}
+  ports:
+    keys:
+    - input
+    values:
+    - _fieldName: input
+      _node: {fileID: 114509033286994848}
+      _typeQualifiedName: System.Object, mscorlib, Version=2.0.0.0, Culture=neutral,
+        PublicKeyToken=b77a5c561934e089
+      connections:
+      - fieldName: vector
+        node: {fileID: 114708853913061688}
+      _direction: 0
+      _connectionType: 1
+      _dynamic: 1
 --- !u!114 &114511978881715272
 MonoBehaviour:
   m_ObjectHideFlags: 0
@@ -27,7 +82,7 @@ MonoBehaviour:
   m_Name: MathNode
   m_EditorClassIdentifier: 
   graph: {fileID: 11400000}
-  position: {x: -401.5, y: -119}
+  position: {x: -472, y: -120}
   ports:
     keys:
     - a
@@ -40,6 +95,7 @@ MonoBehaviour:
         PublicKeyToken=b77a5c561934e089
       connections: []
       _direction: 0
+      _connectionType: 0
       _dynamic: 0
     - _fieldName: b
       _node: {fileID: 114511978881715272}
@@ -47,6 +103,7 @@ MonoBehaviour:
         PublicKeyToken=b77a5c561934e089
       connections: []
       _direction: 0
+      _connectionType: 0
       _dynamic: 0
     - _fieldName: result
       _node: {fileID: 114511978881715272}
@@ -55,7 +112,10 @@ MonoBehaviour:
       connections:
       - fieldName: x
         node: {fileID: 114708853913061688}
+      - fieldName: input
+        node: {fileID: 114245496101350052}
       _direction: 1
+      _connectionType: 0
       _dynamic: 0
   a: 6.48
   b: 7.59
@@ -73,7 +133,7 @@ MonoBehaviour:
   m_Name: Vector
   m_EditorClassIdentifier: 
   graph: {fileID: 11400000}
-  position: {x: -157.5, y: -115}
+  position: {x: -168, y: -120}
   ports:
     keys:
     - x
@@ -89,6 +149,7 @@ MonoBehaviour:
       - fieldName: result
         node: {fileID: 114511978881715272}
       _direction: 0
+      _connectionType: 0
       _dynamic: 0
     - _fieldName: y
       _node: {fileID: 114708853913061688}
@@ -96,6 +157,7 @@ MonoBehaviour:
         PublicKeyToken=b77a5c561934e089
       connections: []
       _direction: 0
+      _connectionType: 0
       _dynamic: 0
     - _fieldName: z
       _node: {fileID: 114708853913061688}
@@ -103,6 +165,7 @@ MonoBehaviour:
         PublicKeyToken=b77a5c561934e089
       connections: []
       _direction: 0
+      _connectionType: 0
       _dynamic: 0
     - _fieldName: vector
       _node: {fileID: 114708853913061688}
@@ -110,44 +173,11 @@ MonoBehaviour:
         Culture=neutral, PublicKeyToken=null
       connections:
       - fieldName: input
-        node: {fileID: 114729867621534192}
+        node: {fileID: 114509033286994848}
       _direction: 1
+      _connectionType: 0
       _dynamic: 0
   x: 0
   y: 2.6412349
   z: 14.33477
   vector: {x: 14.07, y: 2.6412349, z: 14.33477}
---- !u!114 &114729867621534192
-MonoBehaviour:
-  m_ObjectHideFlags: 0
-  m_PrefabParentObject: {fileID: 0}
-  m_PrefabInternal: {fileID: 0}
-  m_GameObject: {fileID: 0}
-  m_Enabled: 1
-  m_EditorHideFlags: 0
-  m_Script: {fileID: 11500000, guid: 98f6f901f0da53142b79277ea3f42518, type: 3}
-  m_Name: DisplayValue
-  m_EditorClassIdentifier: 
-  graph: {fileID: 11400000}
-  position: {x: 104.5, y: -82}
-  ports:
-    keys:
-    - value
-    - input
-    values:
-    - _fieldName: value
-      _node: {fileID: 114729867621534192}
-      _typeQualifiedName: System.Object, mscorlib, Version=2.0.0.0, Culture=neutral,
-        PublicKeyToken=b77a5c561934e089
-      connections: []
-      _direction: 0
-      _dynamic: 0
-    - _fieldName: input
-      _node: {fileID: 114729867621534192}
-      _typeQualifiedName: System.Object, mscorlib, Version=2.0.0.0, Culture=neutral,
-        PublicKeyToken=b77a5c561934e089
-      connections:
-      - fieldName: vector
-        node: {fileID: 114708853913061688}
-      _direction: 0
-      _dynamic: 1

Example/Nodes/DisplayValue.cs

@@ -4,7 +4,7 @@ namespace BasicNodes {
     public class DisplayValue : XNode.Node {
         protected override void Init() {
             base.Init();
-            if (!HasPort("input")) AddInstanceInput(typeof(object), "input");
+            if (!HasPort("input")) AddInstanceInput(typeof(object), ConnectionType.Override ,"input");
         }
 
         public override object GetValue(XNode.NodePort port) {

Scripts/Node.cs

@@ -15,6 +15,13 @@ namespace XNode {
             Always
         }
 
+        public enum ConnectionType {
+            /// <summary> Allow multiple connections</summery>
+            Multiple,
+            /// <summary> always override the current connection </summery>
+            Override,
+        }
+
         /// <summary> Iterate over all ports on this node. </summary>
         public IEnumerable<NodePort> Ports { get { foreach (NodePort port in ports.Values) yield return port; } }
         /// <summary> Iterate over all outputs on this node. </summary>
@@ -49,16 +56,16 @@ namespace XNode {
 
 #region Instance Ports
         /// <summary> Returns input port at index </summary>
-        public NodePort AddInstanceInput(Type type, string fieldName = null) {
+        public NodePort AddInstanceInput(Type type, Node.ConnectionType connectionType = Node.ConnectionType.Multiple, string fieldName = null) {
-            return AddInstancePort(type, NodePort.IO.Input, fieldName);
+            return AddInstancePort(type, NodePort.IO.Input, connectionType, fieldName);
         }
 
         /// <summary> Returns input port at index </summary>
-        public NodePort AddInstanceOutput(Type type, string fieldName = null) {
+        public NodePort AddInstanceOutput(Type type, Node.ConnectionType connectionType = Node.ConnectionType.Multiple, string fieldName = null) {
-            return AddInstancePort(type, NodePort.IO.Output, fieldName);
+            return AddInstancePort(type, NodePort.IO.Output, connectionType, fieldName);
         }
 
-        private NodePort AddInstancePort(Type type, NodePort.IO direction, string fieldName = null) {
+        private NodePort AddInstancePort(Type type, NodePort.IO direction, Node.ConnectionType connectionType = Node.ConnectionType.Multiple, string fieldName = null) {
             if (fieldName == null) {
                 fieldName = "instanceInput_0";
                 int i = 0;
@@ -67,7 +74,7 @@ namespace XNode {
                 Debug.LogWarning("Port '" + fieldName + "' already exists in " + name, this);
                 return ports[fieldName];
             }
-            NodePort port = new NodePort(fieldName, type, direction, this);
+            NodePort port = new NodePort(fieldName, type, direction, connectionType, this);
             ports.Add(fieldName, port);
             return port;
         }
@@ -168,20 +175,30 @@ namespace XNode {
         [AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
         public class InputAttribute : Attribute {
             public ShowBackingValue backingValue;
+            public ConnectionType connectionType;
             
             /// <summary> Mark a serializable field as an input port. You can access this through <see cref="GetInput(string)"/> </summary>
             /// <param name="backingValue">Should we display the backing value for this port as an editor field? </param>
-            public InputAttribute(ShowBackingValue backingValue = ShowBackingValue.Unconnected) { this.backingValue = backingValue; }
+            /// <param name="connectionType">Should we allow multiple connections? </param>
+            public InputAttribute(ShowBackingValue backingValue = ShowBackingValue.Unconnected, ConnectionType connectionType = ConnectionType.Multiple) {
+                this.backingValue = backingValue;
+                this.connectionType = connectionType;                
+            }
         }
 
         /// <summary> Mark a serializable field as an output port. You can access this through <see cref="GetOutput(string)"/> </summary>
         [AttributeUsage(AttributeTargets.Field, AllowMultiple = true)]
         public class OutputAttribute : Attribute {
             public ShowBackingValue backingValue;
+            public ConnectionType connectionType;
 
             /// <summary> Mark a serializable field as an output port. You can access this through <see cref="GetOutput(string)"/> </summary>
             /// <param name="backingValue">Should we display the backing value for this port as an editor field? </param>
-            public OutputAttribute(ShowBackingValue backingValue = ShowBackingValue.Never) { this.backingValue = backingValue; }
+            /// <param name="connectionType">Should we allow multiple connections? </param>
+            public OutputAttribute(ShowBackingValue backingValue = ShowBackingValue.Never, ConnectionType connectionType = ConnectionType.Multiple) {
+                this.backingValue = backingValue;
+                this.connectionType = connectionType;
+            }
         }
 
         [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]

Scripts/NodePort.cs

@@ -13,6 +13,8 @@ namespace XNode {
         public NodePort Connection { get { return connections.Count > 0 ? connections[0].Port : null; } }
 
         public IO direction { get { return _direction; } }
+        public Node.ConnectionType connectionType { get { return _connectionType; } }
+
         /// <summary> Is this port connected to anytihng? </summary>
         public bool IsConnected { get { return connections.Count != 0; } }
         public bool IsInput { get { return direction == IO.Input; } }
@@ -39,6 +41,7 @@ namespace XNode {
         [SerializeField] private string _typeQualifiedName;
         [SerializeField] private List<PortConnection> connections = new List<PortConnection>();
         [SerializeField] private IO _direction;
+        [SerializeField] private Node.ConnectionType _connectionType;
         [SerializeField] private bool _dynamic;
 
         /// <summary> Construct a static targetless nodeport. Used as a template. </summary>
@@ -48,8 +51,14 @@ namespace XNode {
             _dynamic = false;
             var attribs = fieldInfo.GetCustomAttributes(false);
             for (int i = 0; i < attribs.Length; i++) {
-                if (attribs[i] is Node.InputAttribute) _direction = IO.Input;
+                if (attribs[i] is Node.InputAttribute) {
-                else if (attribs[i] is Node.OutputAttribute) _direction = IO.Output;
+                    _direction = IO.Input;
+                    _connectionType = (attribs[i] as Node.InputAttribute).connectionType;
+                }
+                else if (attribs[i] is Node.OutputAttribute) {
+                    _direction = IO.Output;
+                    _connectionType = (attribs[i] as Node.OutputAttribute).connectionType;
+                }
             }
         }
 
@@ -59,16 +68,18 @@ namespace XNode {
             ValueType = nodePort.valueType;
             _direction = nodePort.direction;
             _dynamic = nodePort._dynamic;
+            _connectionType = nodePort._connectionType;
             _node = node;
         }
 
         /// <summary> Construct a dynamic port. Dynamic ports are not forgotten on reimport, and is ideal for runtime-created ports. </summary>
-        public NodePort(string fieldName, Type type, IO direction, Node node) {
+        public NodePort(string fieldName, Type type, IO direction, Node.ConnectionType connectionType, Node node) {
             _fieldName = fieldName;
             this.ValueType = type;
             _direction = direction;
             _node = node;
             _dynamic = true;
+            _connectionType = connectionType;            
         }
 
         /// <summary> Checks all connections for invalid references, and removes them. </summary>
@@ -176,6 +187,8 @@ namespace XNode {
             if (port == this) { Debug.LogWarning("Attempting to connect port to self."); return; }
             if (IsConnectedTo(port)) { Debug.LogWarning("Port already connected. "); return; }
             if (direction == port.direction) { Debug.LogWarning("Cannot connect two " + (direction == IO.Input ? "input" : "output") + " connections"); return; }
+            if (port.connectionType == Node.ConnectionType.Override && port.ConnectionCount != 0) { port.ClearConnections(); }
+            if (connectionType == Node.ConnectionType.Override && ConnectionCount != 0) { ClearConnections(); }
             connections.Add(new PortConnection(port));
             if (port.connections == null) port.connections = new List<PortConnection>();
             if (!port.IsConnectedTo(this)) port.connections.Add(new PortConnection(this));