(Classic) Change node - Setting and triggering variables

With change node, it is possible to save messages that are coming out of the nodes and reuse them.

Open

Open

Use of variable

The context object - stores data inside a single node,

The flow object - stores data for a sing flow tab,

The global object - stores data for the whole logic.

This article will cover knowledge about flow and global objects.

A node used to set the message as a variable is a change node.

It can both, set a flow.variable to msg.payload (1) and
set a msg.payload to flow.variable (2).

(1) To set a variable flow.var_01 as a value of msg.payload:

The value of the variable (var_01) will be overwritten and the value of the original message will be passed on without modification.

For example, if the message with the value “100” will come into a node, it will be saved as a value of a variable.

(2) To change the incoming message into a variable, the “Set” rule has to be used in the other way

Now the output of the change node will be the value which is stored as a variable (var_01).
Every incoming message will be changed into a value of a variable.

Checking the value of variables

The value of the flow is shown in the “context” tab.

Use cases

HCL

In logic when the presence detection has to trigger a value from the Intensity Scheduler (ES_CCT node).

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Turning ON daylight harvesting at a scheduled time.