Access a value on message

General
1

Good afternoon

If is not a bit f abuse can someone help me to access prinTime (as example) on message below in order to get it as mesg.payload?

{"_timestamp": 1557336569, "progress": 43, "printer_data": {"progress": {"completion": 43.0026015784234, "printTimeLeftOrigin": "genius", "printTime": 6544, "printTimeLeft": 8911, "filepos": 5236192}, "state": {"text": "Printing", "flags": {"cancelling": false, "paused": false, "operational": true, "pausing": false, "printing": true, "resuming": false, "sdReady": false, "error": false, "ready": false, "finishing": false, "closedOrError": false}}, "currentZ": 4.1, "job": {"averagePrintTime": 15455.695065021515, "lastPrintTime": 15455.695065021515, "user": "david", "file": {"origin": "local", "name": "Husky_logo_60--PLAx4.gcode", "date": 1557276735, "path": "Husky_logo_60--PLAx4.gcode", "display": "Husky logo 60%-PLAx4.gcode", "size": 12176454}, "estimatedPrintTime": 13151.32884912111, "filament": {"tool0": {"volume": 12.156581574058073, "length": 5054.119170014139}}}, "offsets": {}}, "location": "local", "path": "Husky_logo_60--PLAx4.gcode"}

Thanks in advance

2

Hi @davidcgu

This page the docs explains how to understand the structure of a message and identify the path to any element: https://nodered.org/docs/user-guide/messages

3

The more I try the most lost I am, is an object inside another object inside another object and this is making me a bit crazy in order to understand how to access there.

Sorry

4

If you pass the message to a Debug node, you can explore its structure to find the element you are interested in:

Local_Node-RED
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When you hover over the element you care about, you'll see a pair buttons appear on the right.

Local_Node-RED
Local_Node-RED.png1022×134 13.9 KB

Clicking on the first button will copy the path to the item to your clipboard. In this instance it gives:

payload.printer_data.progress.printTime

Which you can then use directly in a Change node, or add msg. to the beginning if you want to use it in a Function node.

5

Thanks Nick for your help,

In fact this is what make it so difficult for me to understand because on debug message shows me all in a row instead of giving me separated paths.

image
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Regards

6

Hi David,

the page in the docs I linked to says this: Working with messages : Node-RED

If a message property contains a JSON string it must first be parsed to its equivalent JavaScript object before the properties it contains can be accessed. To determine whether a property contains a String or Object, the Debug node can be used.

Node-RED provides a JSON node to do this conversion.

7

I must be an idiot..... had the json conversion for the node but was looking at the debug prior to that what was making me totally confused, now solved, thanks a lot Nick!