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Overview

Once created, a User-Defined Function becomes available anywhere expressions are used in Sift, including Rules, Calculated Channels, and other User-Defined Functions. In the expression editor, User-Defined Functions appear in the Expression Syntax panel under the User-Defined Functions section.

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Using User-Defined Functions in expressions

When defining an expression, you can reference a User-Defined Function just like a built-in function. In the examples below, $1 refers to camera_1.temperature. For example, in a Calculated Channel: 
fl_tutorial_7_user_defined_function($1)
Or in a Rule, as part of a logical condition: 
fl_tutorial_7_user_defined_function($1) > 86
Because User-Defined Functions are defined once and reused across expressions, updating the function’s logic applies the change centrally without requiring updates everywhere it is used.