iLogic Parameter Types

It’s logical to consider that the order of the code in your rule can determine whether it needs to be run twice to complete or not, however there is another cause for this that many people are unaware of and that’s what I will cover today.

The different types of Parameters.

There are two different types of Parameters and they both behave differently which can affect the outcome once a rule has run. This first type is the most common parameter- the “double click the name in the rule editor” blue parameter.

This parameter does what it needs to, including updating in the rule if you rename the parameter in your model. This Parameter will hold onto a value, and only change to that value when the rule finishes executing.

This characteristic of the blue parameter can cause problems.

Let’s examine the example below.

If I know Frame_Width is 100 when my rule starts, I expect the code to make the Length of the Horizontal_SHS component 200. But that’s not the case. The reason for that is after changing the Frame_Width to 200, we now know it will hold that value until the rule finishes, then update to 200. As a result, the Frame_width that is used to drive the length of the SHS part is still 100. Running the rule a second time will cause Frame_Width to be the expected 200 and the component will update correctly.

There is a way around this characteristic, and here Parameter type becomes useful.

Enter the Purple and green parameter, technically referred to as a “Dynamic Parameter”. This parameter uses a String indicated by the “Quotation marks” and won’t update on its own if you change the name of the parameter. On the surface they play the same role, however the dynamic Parameter alters the outcome.

If I was to run the same code but using a dynamic parameter instead of the normal blue parameter, we would get the desired result the first time.

The reason for that is a dynamic Parameter forces the parameter to take the new value as soon as its set instead of waiting for the end of the rule. After the first line, Frame_Width will be 200, and as a result the Length of the SHS part will be 200.

If you find your rules need to run twice, check the order of the code in the rule remembering it runs top to bottom followed by what type of parameters are getting the values needed to execute correctly. For tricky cases, combine your checks with the iLogic Logger in my previous Episode.

With each Inventor release, Autodesk adds new features and abilities in iLogic, so if you’ve used it before or considering using it, contact us. We provide various iLogic training from the very basics to more tailored courses to help you get up to speed with iLogic.