Add write support with automatic type coercion to OpcUaMonitoredNode

writeValue() Q_INVOKABLE coerces QML JS types to the exact C++ type
expected by the OPC UA node (auto-detected from DataType attribute via
opcUaDataTypeToQOpcUaType). Handles all scalar types, booleans, and
comma-separated array input. Adds writable property derived from
AccessLevel bits. Demo shows inline TextField + Write button for
writable nodes, "(READ-ONLY)" for others.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/OpcUaMonitoredNode.h b/src/OpcUaMonitoredNode.h
index ac5983a..5895bea 100644
--- a/src/OpcUaMonitoredNode.h
+++ b/src/OpcUaMonitoredNode.h
@@ -57,6 +57,7 @@ class OpcUaMonitoredNode : public QObject, public QQmlParserStatus
   Q_PROPERTY (
       bool monitored READ monitored WRITE setMonitored NOTIFY monitoredChanged)
   Q_PROPERTY (QVariant value READ value NOTIFY valueChanged)
+  Q_PROPERTY (bool writable READ writable NOTIFY writableChanged)
   Q_PROPERTY (OpcUaNodeInfo info READ info NOTIFY infoChanged)
 
 public:
@@ -69,8 +70,19 @@ public:
   void setMonitored (bool monitored);
 
   QVariant value () const;
+  bool writable () const;
   OpcUaNodeInfo info () const;
 
+  /**
+   * @brief Write a value to the OPC UA node.
+   *
+   * Coerces @a value to the node's data type (auto-detected from the
+   * server's DataType attribute).  For array nodes, a comma-separated
+   * string is split and each element coerced individually.
+   * Result is reported asynchronously via writeCompleted().
+   */
+  Q_INVOKABLE void writeValue (const QVariant &value);
+
   void classBegin () override;
   void componentComplete () override;
 
@@ -78,23 +90,30 @@ signals:
   void nodeIdChanged ();
   void monitoredChanged ();
   void valueChanged ();
+  void writableChanged ();
   void infoChanged ();
+  void writeCompleted (bool success, const QString &message);
 
 private slots:
   void handleAttributeUpdated (QOpcUa::NodeAttribute attr,
                                const QVariant &value);
   void handleValueUpdated (const QVariant &value);
   void handleClientConnectedChanged ();
+  void handleAttributeWritten (QOpcUa::NodeAttribute attr,
+                               QOpcUa::UaStatusCode statusCode);
 
 private:
   void setupNode ();
   void teardownNode ();
+  QVariant coerceValue (const QVariant &input) const;
 
   QString m_nodeId;
   bool m_monitored = true;
   bool m_componentComplete = false;
 
   QOpcUaNode *m_node = nullptr;
+  QOpcUa::Types m_valueType = QOpcUa::Types::Undefined;
+  bool m_writable = false;
   QVariant m_value;
   OpcUaNodeInfo m_info;
 };