opcua::ValueCallbackBase Class Reference

#include <nodestore.hpp>

Inheritance diagram for opcua::ValueCallbackBase:

Detailed Description

Value callback base class for variable nodes.

Value callbacks allow to synchronize a variable value with an external representation. The attached callbacks are executed before every read and after every write operation.

See also

https://www.open62541.org/doc/1.3/tutorial_server_datasource.html

Examples

server_valuecallback.cpp.

Definition at line 18 of file nodestore.hpp.

Public Member Functions
virtual void	onRead (Session &session, const NodeId &id, const NumericRange *range, const DataValue &value)=0
virtual void	onWrite (Session &session, const NodeId &id, const NumericRange *range, const DataValue &value)=0
UA_ValueCallback	create (bool ownsAdapter) override
Public Member Functions inherited from opcua::PluginAdapter< UA_ValueCallback >
	PluginAdapter ()=default
	PluginAdapter (const PluginAdapter &)=default
	PluginAdapter (PluginAdapter &&) noexcept=default
virtual	~PluginAdapter ()=default
PluginAdapter &	operator= (const PluginAdapter &)=default
PluginAdapter &	operator= (PluginAdapter &&) noexcept=default

Additional Inherited Members
Public Types inherited from opcua::PluginAdapter< UA_ValueCallback >
using	PluginType

Member Function Documentation

onRead()

virtual void opcua::ValueCallbackBase::onRead ( Session & session, const NodeId & id, const NumericRange * range, const DataValue & value )

pure virtual

Called before the value attribute is read.

It is possible to write into the value attribute during onBeforeRead (using e.g. services::writeValue or Node::writeValue). The node is re-opened afterwards so that changes are considered in the following read operation.

Parameters

session	Current session
id	The identifier of the node being read from
range	Optional numeric range the client wants to read from
value	Current value before the read operation

Examples

server_valuecallback.cpp.

onWrite()

virtual void opcua::ValueCallbackBase::onWrite ( Session & session, const NodeId & id, const NumericRange * range, const DataValue & value )

pure virtual

Called after writing the value attribute.

The node is re-opened after writing so that the new value is visible in the callback.

Parameters

session	Current session
id	The identifier of the node being written to
range	Optional numeric range the client wants to write to
value	New value after the write operation

Examples

server_valuecallback.cpp.

create()

UA_ValueCallback opcua::ValueCallbackBase::create ( bool ownsAdapter )

overridevirtual

Implements opcua::PluginAdapter< UA_ValueCallback >.