MethodNode Class Reference

Represents an OPCUA method node. More...

Inherits BaseNode.

Public Member Functions
None	add_argument (self, str name, int in_out_type, int data_type, Union[str, int, float] default_value)
	Adds an argument to the method. More...
None	call (self)
	Starts execution of the method on the server. More...
None	create (int namespace_index, str name, cvb.opcua.NodeID parent_node_id)
	Creates an OPCUA method object. More...
None	deregister_callback (self, cvb.EventCookie event_cookie)
	Deregisters a callback. More...
List[cvb.opcua.MethodNodeArgument]	input_arguments (self)
	Returns all registered input arguments. More...
List[cvb.opcua.MethodNodeArgument]	output_arguments (self)
	Returns all registered output arguments. More...
cvb.EventCookie	register_read_callback (self, Callable[[Any], Any] callback)
	Registers a callback for the call/execute operations. More...
Public Member Functions inherited from BaseNode
List[cvb.opcua.NodeID]	browse (self, cvb.opcua.BrowseFilter filter_options)
	Enumerates the child nodes present in the OPCUA server. More...
Union[int, float, str]	get_attribute (self, int attribute_id)
	Gets specific information about this node. More...
cvb.opcua.NodeID	node_id (self)
	Gets the OPCUA node ID of this node. More...
None	set_attribute (self, int attribute_id, Union[int, float, str] value)
	Sets specific information about this node. More...

Additional Inherited Members
Properties inherited from BaseNode
	access = property
	int: Gets access rights to this node (see cvb.opcua.Access).
	browse_name = property
	str: Gets the browse name of this node.
	connection_status = property
	int: Gets connection status of this node (see cvb.opcua.ConnectionStatus).
	description = property
	str: Gets description of this node.
	display_name = property
	str: Gets the human-readable name of this node.
	node_class = property
	int: Gets OPCUA node class of this node (see cvb.opcua.NodeClass).

Detailed Description

Represents an OPCUA method node.

It provides an interface for calling functions/methods on the OPCUA server. It may have input and output arguments. A typical usage consists of the following steps:

1. On the server-side: A MethodNode is created and added to the server.
2. On the server-side: The desired amount of arguments is added via the MethodNode.add_argument method for input and output. This 'defines' the arguments.
3. On the server-side: A callback is set. This is later called by the client via the call method.
4. On the client-side: The client application retrieves the MethodNodes and retrieves the arguments via the MethodNode.input_arguments method.
5. On the client-side: The client application sets the input arguments to the desired value and then calls the MethodNode.call method.
6. On the server-side: The callback is triggered. 6.a. The server application, inside the callback, retrieves the input arguments by using the MethodNode.input_arguments method and does whatever the callback is supposed to do. 6.b. The server application, still inside the callback, sets the output arguments by calling the MethodNode.output_arguments method.
7. The client application retrieves the output arguments.

Member Function Documentation

add_argument()

None add_argument	(		self,
		str	name,
		int	in_out_type,
		int	data_type,
		Union[str, int, float]	default_value
	)

Adds an argument to the method.

Parameters

name : str Name of the argument.

in_out_type : int The argument an output/input argument.

data_type : int Data format of the argument.

default_value : Union[str, int, float] Default of the argument.

call()

None call

(

self

)

Starts execution of the method on the server.

See class description for details.

create()

None create	(	int	namespace_index,
		str	name,
		cvb.opcua.NodeID	parent_node_id
	)

Creates an OPCUA method object.

Parameters

namespace_index : int String literal for a non-localized, human-readable name of an OPCUA node.

name : str String literal for non-localized, human-readable name of the OPCUA node.

parent_node_id : cvb.opcua.NodeID OPCUA node ID of the parent to which the OPCUA node to be created belongs.

deregister_callback()

None deregister_callback	(		self,
		cvb.EventCookie	event_cookie
	)

Deregisters a callback.

The usage of lambdas for data access is highly recommended. Note: The callback MUST be deregistered, otherwise internal object handles will not be closed.

Parameters

event_cookie : cvb.EventCookie Event cookie, obtained from registering the listener.

input_arguments()

List[cvb.opcua.MethodNodeArgument] input_arguments

(

self

)

Returns all registered input arguments.

See class description for details.

Returns

List[cvb.opcua.MethodNodeArgument] All registered input arguments.

output_arguments()

List[cvb.opcua.MethodNodeArgument] output_arguments

(

self

)

Returns all registered output arguments.

See class description for details.

Returns

List[cvb.opcua.MethodNodeArgument] All registered output arguments.

register_read_callback()

cvb.EventCookie register_read_callback	(		self,
		Callable[[Any], Any]	callback
	)

Registers a callback for the call/execute operations.

The usage of lambdas for data access is highly recommended. Note: The callback MUST be deregistered, otherwise internal object handles will not be closed.

Parameters

callback : Callable[[Any], Any] A callable as a callback to be registered.

Returns

cvb.EventCookie Cookie for unregistering the callback.