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Expression Variable Condition

The Expression Variable condition tests the value of a specified Expression in the current ReactorSensor.

An Expression Variable condition

It is possible to make both string and mathematical comparisons. It is also possible to use variable references in the operand(s) (e.g. {varname}). All of the same operators available to Device State conditions are available with the following exceptions:

  1. The updates operator used with Device State actions is not available;
  2. The is NULL operator may be used to detect null expression results (you can also compare to an empty string because null is coerced to an empty string for string comparisons, but doing that you then cannot differentiate between an empty string an null).

The expression/variable must exist at the time the condition is created. You will need to visit the Expressions tab to create your variable prior to creating an instance of this condition type.

If you want to test an expression/variable in a different ReactorSensor, use the Device State condition. The expression must also be marked for export in that ReactorSensor.

It's a Short-cut

The Expression Variable condition is largely a shortcut for a Device State condition to access an expression/variable in the current ReactorSensor. It is faster and more efficient, and should be used in preference to the Device State condition in those conditions.