Getting value from a JSON point

[a3pl1]

Hi,

I'm getting some point values from MQTT source and that value is in string and JSON format.
So for example I have point temp with value: {"readTime":"2025-02-12T12:00:00","place":"kitchen", "value":"21"}

Can I script or do something to get a point with value=21 for presentations and charts in SCADA LTS ?

[fabiodurao]

Hello,

It is possible to do this conversion using a meta datapoint.

1 - First, create this mqtt datapoint that returns this json in string;
2 - Create a meta datasource and then a datapoint with the name "kitchen" for example;
3 - In this datapoint, set it as numeric, add the mqtt datapoint created in item 1, within the context and give it a nickname "kitchen";
4 - Use the following script to convert the string to json and return only the value;

const jsonString = kitchen.value;
const jsonObject = JSON.parse(jsonString); // Convert a string to JSON object

const valueAsNumber = Number(jsonObject.value);
return valueAsNumber; // Return 21 how number

5 - Click on the green circle to the left of the script to test if it is working as intended, it will show the result below, as in the image;

I did a simulation bringing your json into a string variable that I had. See below:

Note: Now you will have a new datapoint, it will assume the desired value and no longer the mqtt datapoint, the mqtt will only have the json. It is important to keep in mind that if you need to write to this datapoint, you will have to do a little more work, something like creating a virtual datapoint to receive the desired value, a meta datapoint converting from numeric to json and point link taking the json to the mqtt datapoint, but you will probably only need to read, and the solution above will be enough.

[a3pl1]

Working great :)
Thank You.