How to match on union JSON similar to Typescript

[elibarber]

Example 1:

{
"kind": "label",
"value": "this is the label"
}

Example 2:
{
"kind": "command",
"value": 32,
"step": 5,
"message": "message"
}

I was using the BlueSerialization package from blue origin. But am am running into this issue.

In typescript I can union between different interfaces and match on the "kind" value which is essentially a string enum. 
https://medium.com/@meetpujara02/understanding-union-types-in-typescript-a-deep-dive-36b27eeae808 

How can i mirror this behavior in labview? Essentially the payload is json and it can look different. What is considered best practice? In my case, I will actually be receiving an array of these payloads. Each one can be different in the array. How can i safely match on each to ensure the payload is valid?

thank you,

[Kyle97330]

There is this JSON parser:

https://www.ni.com/en/support/downloads/tools-network/download.jsontext.html#405275

It includes a (limited) form of JSONPath to work with JSON.

https://jsonpath.com/

I have not used the JSONPath portion of it personally but it sounds like that might be what you're looking for.

[BertMcMahan]

I think the JSONText library has JSON Schema support, which is intended to validate incoming JSON. I believe the JSON Schema enum type would do what you're looking for: https://json-schema.org/understanding-json-schema/reference/enum

[raphschru · Accepted solution]

Hi elibarber,

Union types do not exist as you have in TypeScript.

The closest I can see would be:

 - A variant containing a cluster, specific to the kind of payload ;

 - A string containing a flattened/binary version of the same cluster ;

 - A class hierarchy with a subclass for each kind of payload.

I would personally choose the class hierarchy for scalability, but it can be a challenge for new LabVIEW users.

Attached is an example where I used the JSONtext toolkit function with a custom Object Serializer to deserialize an array of mixed type objects.

Regards,

Raphaël.

[elibarber]

Wow. Insane. OOP is not my strength with LabVIEW, but I was able to recreate or example with 30 classes for each command and it works! 

Thank you, this is perfect. I know I will need need to plan for future payloads and this is should scale perfectly for when that time comes.

[raphschru]

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@elibarber wrote:

Thank you, this is perfect. I know I will need need to plan for future payloads and this is should scale perfectly for when that time comes.

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