JSON parsing error (Variant To Data in i3-json.lvlib:Get Object Parameter - String.vi)

[bim4]

Hi,

I'm using the i3 json toolkit for LabVIEW : https://forums.ni.com/t5/JSON-Toolkit-for-LabVIEW/gp-p/8520?start=0&view=discussions

I'm facing an error when using the json below and trying to get the "cmd" value :

{"cmd":{"module":"test1","name":"Session"}}

Get Object parameter VI returns :

Variant To Data in i3-json.lvlib:Get Object Parameter - String.vi->RS_GetJsonElement.vi

This case seems basic so I might be mistaking somehow.

Does any one get the same issue using this library, and is there a way to fix it?

Thanks in advance for your support,

Bim

[bim4]

Attached vi snapshot

[MilanR]

Hi Bim,

In the example JSON provided it can be thought of as follows:

A JSON object with one parameter. That parameter is named cmd.

The cmd parameter is a JSON object with two parameters. The parameters are module and name.

The module parameter is a string with value "test1".

The name parameter is a string with value "Session".

In the VI screenshot the parameter cmd was read as a String which returned an error because the cmd parameter is a JSON object. To extract the cmd parameter you have to read it as a JSON object. To then read module and name parameters you have to look them up from the cmd JSON object:

[MilanR]

If you are using LabVIEW 2013 or greater you may also consider using the Unflatten From JSON primitive built into LabVIEW instead:

Unflatten from JSON generally gives better performance and can be easier to use in many cases.

[bim4]

Hi Milan,

Many thanks for your feedbacks. Actually I was expecting it to manage both cases and result a string that could be the flattened json as string.

I'll build for the moment a specific vi for my basic need as this dependency on the input json form is blocker.

Thanks,

BR,

Bim

[MilanR]

You can use the Encode JSON vi to serialize a JSON Object back into a string encoded as JSON. The following shows how the cmd parameter is retrieved and serialized into a JSON string.

[bim4]

Hi Milan,

Great example, I was missing something and now it's clear.

Many thanks for your support!

Bim