Making use of Hidden Parameters in FeatureScript

A parameter in an Onshape Custom Feature can be made hidden from the user by using a UIHint

And this can lead to some interesting uses! But first we need an editing logic function. The editing logic function triggers when a feature is first created and whenever a user modifies an input. The function allows you to edit the definition of the feature before the main body of the feature runs, but it also updates the definition for the user. The intention is to allow for "intelligent default values". But we can also use it for some more advanced functionality.

Array item labels

The label for an array item can be set to the value of one of the parameters with the pattern shown in the default code:

The item label template sets the label of the array item to the values mapped with #parameterName. But the parameter doesn't need to be visible! By adding a hidden string parameter, and setting the Item Label Template to its value, we can create custom labels for each item. We can use editing logic to dynamically generate intelligent item labels.

Example

A simple example - automatic indices. In the editing logic, we can set the hidden value to the index in the array. Every time the array changes, editing logic updates automatically - keeping the indices accurate and up to date.

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