how to receive two output value in a function node in node-red

[svinot...@gmail.com]

In node red application I am used exec node for getting the mac address and same time using sq-lite database for get the values. I need to get the mac database node output and get mac from device node output in Get mac function. Is it possible to get the two output in one function.

[Colin Law]

You can use the join node in manual mode setting it to Create a key value object and send the message after 2 message parts and (probably) Every subsequent message.  Make sure the two inputs have different topics then you will get a payload with the two values which you can access in a function (or other) node.

Colin

On 23 January 2018 at 13:33, <svinot...@gmail.com> wrote:

In node red application I am used exec node for getting the mac address and same time using sq-lite database for get the values. I need to get the mac database node output and get mac from device node output in Get mac function. Is it possible to get the two output in one function.

--
http://nodered.org
 
Join us on Slack to continue the conversation: http://nodered.org/slack
---
You received this message because you are subscribed to the Google Groups "Node-RED" group.
To unsubscribe from this group and stop receiving emails from it, send an email to node-red+unsubscribe@googlegroups.com.
To post to this group, send email to node...@googlegroups.com.
Visit this group at https://groups.google.com/group/node-red.
To view this discussion on the web, visit https://groups.google.com/d/msgid/node-red/18de9e9c-4a65-4764-8b37-9ffaf13bd143%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Grant Parks]

One way I do this is to use a node context variable (so far this only works when I'm expecting exactly 2 msg inputs like you describe).

In function node:

const savedData = context.get('saved');
if (savedData) {
    // We now have both msgs
    var mergedData = Object.assign({}, msg.payload, savedData);
    context.set('saved', null);
    // Do what you want with it
    return mergedData;
}
else {
    context.set('saved', msg.payload);

[steve rickus]

It is generally easier and safer to chain those two functions together into one serial flow -- this avoids having to use context to hold values while waiting for the rest of the information to be generated.

Try calling the exec cmd first -- wire that to a change node, and "Move" msg.payload to somewhere else, like msg.mac -- wire that to the db query, which should put its output into msg.payload. The output msg should now contain msg.mac and msg.payload in a single msg object.

The exception may be when two unrelated, async api calls need to be kicked off in parallel -- especially when one may run much longer than the other. But your two steps should run in milliseconds, not minutes. And since node-red (and nodejs) is single-threaded, trying to run two synch functions in parallel paths does not run any faster anyway.

--

Steve