Getting values from JSON

I have begun my journey into gamma (again) by trying to read values from a json file. I am getting a bit of success, but it is not quite like I want it.

My problem is that i need the value in the field “Vaerdi” when I have a certain “AnalysetypeId” see attached zip for patch and a sample json file. I do get that, but besides the correct slices, I also get empty slices.

I also feel that I am not doing this in an optimal way.

So any advice on how I can just get the slices that have the right content? (5.9 KB)

as for empty slices, you can use the Keep pin to filter those out. see this video towards the end:

1 Like

You could use XPathGetValues with this query : /Svaroversigt/Svaroversigt/Laboratorieresultater[AnalysetypeId="iupac_NPU03568"]/Vaerdi. You would retrieve all the Vaerdi where AnalysetypeId is iupac_NPU03568.

Pro tip : there is a Visual Studio Code plugin called XML Tools that allows you to highlight some portion of an XML document and automagically give you the correct XPath query to retrieve it.


just to add to @sebescudie’s Pro Tip, you can do the same in chrome or Firefox by using the dev tools (Ctrl+Shift+I in FF), then navigating to the specific element and selecting, then: right click/Copy/XPath:




I am actually using keep. I get a spread of the same size as the input but with empty slices.

@sebescudie and @ravazquez am having a JSON file, not XML.

it seems like the xpath query doesn’t work here. I might be doing something wrong

@ravazquez you made something for me i think two years ago. I am now trying to recreate that in VL.

1 Like

The following expression works:

JSON-reader.vl (13.5 KB)

1 Like

Hey @sunep, I do remember cooking up some regex or similar for you in the past, glad to hear you are porting it to gamma : ) .

Have you looked at the “Read JSON” help patch? It shows how you get an XDocument from a JSON file, you can then use XPath to navigate and get what you need as if it was XML:


You don’t have to do it like that, but the nodes are there and it’s relatively straightforward.

Hope that helps.

1 Like

Concerning the Keep: Use the condition from the inner foreach in the outer one too.

1 Like

Thanks guys.
I can see that it makes sense. I need to use more time in Gamma to become more fluent.

One more thing TryParse fails (at least on my system) when a comma is used as decimal separator.
So when you want to convert the strings to float you maybe have too replace it with a dot beforehand.

how weird, got it working here :

reg. XML, as you can see on my screenshot, using ToString on an XDocument (which is the output type of JSONReader) gives you an XML string.

ah cool, nice one!


@bjoern Thanks a lot. I have now also fitered out elements that are failed responses. thanks a lot. Now I have something that is almost elegant and very usable.

1 Like

This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.