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EMPTY Entity

Feature Since Version Notes
EMPTY or "" 1.0 Represents a null or empty value

The EMPTY entity signifies the absence of a value. It is most commonly used for checking if a topic currently holds any data.

LOT treats EMPTY and an empty string literal ("") as equivalent in comparisons.

Usage

Primarily used in IF conditions to check if a GET TOPIC result is empty.

Syntax

EMPTY

Alternatively, an empty string can be used for comparison:

""

Examples

1. Initializing a Topic Value:

DEFINE ACTION InitializeCounter
ON TOPIC "system/start" DO
    IF GET TOPIC "persistent/counter" == EMPTY THEN
        PUBLISH TOPIC "persistent/counter" WITH 0
    ENDIF

2. Checking for Configuration:

DEFINE ACTION CheckConfig
ON EVERY 1 MINUTE DO
    IF GET TOPIC "config/device_id" = "" THEN
        PUBLISH TOPIC "log/error" WITH "Device ID not configured!"
    ELSE
        // Proceed with normal operation
    ENDIF

Related Documentation