Call method with extensionObject as Argument

[BenediktEnger]

Hi,

I'm trying to call a method which has a ExtensionObject as Input Argument. Unfortunally, I can't find out, how to pass this argument to the method call_method() the right way.
The problem is, I don't know how to get the variantType of the object.
I checked the extension objects stored after calling load_data_type_definitions() but the object I'm looking for is not part of it.

Strange is: I have Siemens PLC OPC UA Server and the structure I'm looking for is nested in a generic structure:

I hope somebody can help me. Thanks!

[schroeder-]

This is how it should work:

arg1 = ua.SK2_AmsMeasurementStatusType()
obj.call_method(method_id, arg1)

If load_data_type_definitions does not return the node for those class we holes in load_data_type_definitions.
Which version are you using? Because I did some fixes for load_data_type_definitions in master (#901)
Also is there something in the logging?

[BenediktEnger]

This seems to work. When I call client.load_data_type_definitions(), the structures are read.
The problem is now, that in one structure I use a String. Don't ask me why, but Siemens is not using the String node from namespace 0, but they are creating there own Node:

Because it is no extension object, it will not be found and the following code crashes. (structures104.py line 186)

if sfield.DataType.NamespaceIndex == 0 and sfield.DataType.Identifier in ua.ObjectIdNames:
            if sfield.DataType.Identifier == 24:
                uatype = "Variant"
            elif sfield.DataType.Identifier == 22:
                uatype = "ExtensionObject"
            else:
                uatype = ua.ObjectIdNames[sfield.DataType.Identifier]
        elif sfield.DataType in ua.extension_objects_by_datatype:
            uatype = ua.extension_objects_by_datatype[sfield.DataType].__name__
        elif sfield.DataType in ua.enums_by_datatype:
            uatype = ua.enums_by_datatype[sfield.DataType].__name__
        else:
            # FIXME: we are probably missing many custom tyes here based on builtin types
            # maybe we can use ua_utils.get_base_data_type()
            raise RuntimeError(f"Unknown datatype for field: {sfield} in structure:{struct_name}, please report")

When I read the FIXME note, the problem seems to be known. Unfortunally, the described function seems not to exist.
Can you help me with this problem? Thanks

[schroeder-]

In the current master this code is alread reworked:

opcua-asyncio/asyncua/common/structures104.py

Lines 197 to 206 in 0d006fc

	elif sfield.DataType in ua.extension_objects_by_datatype:
	uatype = ua.extension_objects_by_datatype[sfield.DataType].__name__
	elif sfield.DataType in ua.enums_by_datatype:
	uatype = ua.enums_by_datatype[sfield.DataType].__name__
	elif sfield.DataType in ua.basetype_by_datatype:
	uatype = ua.basetype_by_datatype[sfield.DataType]
	else:
	if log_error:
	logger.error(f"Unknown datatype for field: {sfield} in structure:{struct_name}, please report")
	raise RuntimeError(f"Unknown datatype for field: {sfield} in structure:{struct_name}, please report")

As #949 is merged into master both fixes are in master now.

[BenediktEnger]

Thanks. The current master works.
But there where two issues I had to fix:

1. The function register_basetype is writing the class_type as value at basetype_by_datatype.
   This is not working because when getting the default value of the attribute (default_value = get_default_value(uatype) at strucutres104.py l. 211), a name is expected.

    """
    Register a new allias of basetypes for automatic decoding and make them available in ua module
    """
    logger.info("registring new basetype alias: %s %s %s", name, nodeid, class_type)
    basetype_by_datatype[nodeid] = name #NOT class_type
    basetype_datatypes[class_type] = nodeid
    import asyncua.ua

    setattr(asyncua.ua, name, class_type)

2. When creating the code at strucutures104.py l. 179, the node id has to be sorrounded by ' instead of " because there are " sometimes in the node id:

 code = f"""

@dataclass
class {struct_name}{base_class}:

    '''
    {struct_name} structure autogenerated from StructureDefinition object
    '''

    data_type = ua.NodeId.from_string('{data_type.to_string()}')

"""

[schroeder-]

Problem 1 is a quick fix no problem.

The issue with quotes in opc ua names is tricky see issue #783, there is a outstandig pr that tried to fix it: #784

[schroeder-]

Created #954 for register_basetype