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JoelBender / bacpypes

BACpypes provides a BACnet application layer and network layer written in Python for daemons, scripting, and graphical interfaces.
MIT License
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WriteProperty() vs. direct assignment (COVserver.py) #442

Closed villeilkkala closed 2 years ago

villeilkkala commented 2 years ago

Studying COVserver.py example, I can see two ways of assigning a new value to the presentValue property.

In the do_write() function the assignment of the new value is handled with the WriteProperty method: obj.WriteProperty(property_name, value)

in the TestAnalogValueThread() class the assignment of the new value is done directly: test_av.presentValue = next_value.

Looking at the implementation, the WriteProperty() seems to have a lot of error handling. Replacing the direct assignment from the TestAnalogValueThread() class with WriteProperty() also works the same.

In what scenarios should I use WriteProperty() and when do direct assignments?

JoelBender commented 2 years ago

The difference is to test what happens when the property value is changed internally (like x.y = 3 in some code someplace) vs what happens when the change comes from an external source via WriteProperty request. You can do one or the other, they should behave similarly. The extra error checking is avoided in the "direct assignment" case, assuming the developer using the library is setting property values to their correct type and value.

villeilkkala commented 2 years ago

thanks, this is clear.