Overriding Properties in UDT Instances by system.tag.writeAsync()

Ignition
20

Here’s a function you can use instead of system.tag.writeAsync to override properties. It builds the structure in the second code block example in earlier post above, and works for any nesting depth.

# Override a property at variable nesting within a UDT.
# Provide basePath that UDT is in, and path to property from there.
# Property path must contain the property's tag name (i.e. "OVR.enabled", not "enabled").
def tagPropertyOverride(basePath, tagPropertyPath, overrideValue):
	names = tagPropertyPath.replace('.','/').split('/')
	# Cut property from names.
	overrideProperty = names.pop(len(names)-1)
	tags = None
	# Build structure from deepest nesting level up.
	for name in reversed(names):
		if tags is None:
			# This is the innermost level; include property override.
			tags = [{'name':name, overrideProperty:overrideValue}]
		else:
			# Nest last level inside this one and add name for this level.
			tags = [{'name':name, 'tags':tags}]
	# Merge this override with existing tag.
	system.tag.configure(basePath, tags, 'm')

tagPropertyOverride('[default]DPB', 'PI05051/CMD/OVR.enabled', False)

EDIT: For future readers, if you don’t need the ability to work to various nesting depths for a particular base path, see this post for a simpler solution (direct replacement for tag write) to override a property at a path.

4 Likes