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SET Functional Keyword

Feature Since Version Notes
SET >v1.5.6 Defines temporary variables

1. Overview

  • Description: Defines a temporary variable within the current execution scope (e.g., within a single run of an ACTION's DO block). Variables created with SET are not persistent across different trigger events.

2. Signature

  • Syntax: 
    SET "<variableName>" = <value>
// or
SET "<variableName>" WITH <value> // 'WITH' is often used interchangeably with '='

3. Parameters

  • "<variableName>": The name of the temporary variable to define (string).
  • <value>: The value to assign. Can be a literal, an Entity, the result of GET TOPIC, or an Expression.

4. Accessing Variables

Once set, variables are accessed by enclosing the variable name in curly braces {}.

PUBLISH TOPIC "output" WITH {myVariable}
IF {counter} > 10 THEN ...

5. Usage Examples

Basic Example

Set a variable and use it in a publish command.

DEFINE ACTION ProcessData
ON TOPIC "input/data" DO
    SET "processedValue" = (PAYLOAD * 10)
    PUBLISH TOPIC "output/processed" WITH {processedValue}

Intermediate Example

Retrieve topic values, store them in variables, perform calculations, and publish the result.

DEFINE ACTION CalculateSum
ON TOPIC "trigger/calculate" DO
    SET "valueA" = GET TOPIC "inputs/a"
    SET "valueB" = GET TOPIC "inputs/b"

    // Check if values were retrieved successfully
    IF {valueA} != EMPTY AND {valueB} != EMPTY THEN
        SET "sumResult" = {valueA} + {valueB}
        PUBLISH TOPIC "outputs/sum" WITH {sumResult}
    ELSE
        PUBLISH TOPIC "log/error" WITH "Missing input value(s)"
    ENDIF

Advanced Example

Using variables to build a dynamic topic path and message.

DEFINE ACTION DynamicPublish
ON TOPIC "device/+/event" DO
    // Assuming payload is the device ID, e.g., "sensor01"
    SET "deviceID" = PAYLOAD
    SET "targetTopic" = "processed/" + {deviceID} + "/status"
    SET "messageContent" = "Device " + {deviceID} + " reported event at " + TIMESTAMP "ISO"

    PUBLISH TOPIC {targetTopic} WITH {messageContent}

6. Notes & Additional Information

  • Variables defined by SET are temporary and local to the current action execution.
  • They are useful for breaking down complex logic, storing intermediate results, or improving readability.
  • Use KEEP TOPIC if you need to store state persistently between action executions.