How to add an object in array on parsed JSON?

Question

I have this file .json:

{
  "topologyTypes": {
    "stations": {
      "instances": [
        {
          "@name": "value1",
          "@address": "value2"
        },
        {
          "@name": "value3",
          "@address": "value4"
        }         
      ]
    }
  },
  "agg": {},
  "inter": {}
}

I want to add an object like this in topologyType.stations.instances with PowerShell

{
    "@name": "value4",
    "@adress": "value5"
}

So I tried this following code in PowerShell, but it doesn't work:

$path = "./data.json"
$jsonFile = Get-Content $path -Raw | ConvertFrom-Json

$jsonContent = @"
    {
        "@name": "value4",
        "@adress": "value5"
    }
"@

$jsonFile.topologyTypes.stations.instances |
    Add-Content -Value (ConvertFrom-Json $jsonContent)

The desired output I would like to get is like this:

{
  "topologyTypes": {
    "stations": {
      "instances": [
        {
          "@name": "value1",
          "@address": "value2"
        },
        {
          "@name": "value3",
          "@address": "value4"
        },
        {
          "@name": "value4",
          "@address": "value5"
        }         
      ]
    }
  },
  "agg": {},
  "inter": {}
}

"it doesn't work" is an insufficient problem description. How exactly does it "not work"? Are you getting an error? What is the expected and actual result? At first glance I can spot at least one PowerShell and one JSON syntax error. — Ansgar Wiechers
– Ansgar Wiechers, Commented Feb 3, 2018 at 14:59
Hi, thanks for the reply. I got this error : ConvertFrom-Json : invalid json primitive : [. (system.argunment.exception) + ... ations.instances | Add-Content -Value (ConvertFrom-Json $jsonContent) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [ConvertFrom-Json], ArgumentException + FullyQualifiedErrorId : System.ArgumentException,Microsoft.PowerShell.Commands.ConvertFromJsonCommand — J. Sam
– J. Sam, Commented Feb 3, 2018 at 15:09
Because the trailing comma in $jsonContent makes the JSON string invalid. But even if you remove it, you can't insert the new data into the JSON structure by appending to a file. Even the original JSON string you posted is invalid. Please edit your question show a minimal reproducible example of your code, the input, the desired output, and the arror that code gives you. — Ansgar Wiechers
– Ansgar Wiechers, Commented Feb 3, 2018 at 15:47
Ok so i modified my first post sorry.. Im not good with the syntax of json file — J. Sam
– J. Sam, Commented Feb 3, 2018 at 18:03
maybe just string replace [ with [ + $jsonContent before parsing it — Slai
– Slai, Commented Feb 3, 2018 at 18:12

Ansgar Wiechers · Accepted Answer · 2018-02-03 19:53:44Z

6

Define the new content as a PowerShell custom object:

$jsonContent = [PSCustomObject]@{
    '@name'   = 'value4'
    '@adress' = 'value5'
}

append it to the instances substructure of your imported JSON data:

$jsonFile.topologyTypes.stations.instances += $jsonContent

then convert the data back to a JSON string:

$jsonFile | ConvertTo-Json -Depth 4

Note that ConvertTo-Json inserts a lot of intention space. If you want exactly the format you posted you need to do some pretty-printing yourself. Something like this might help.

edited Feb 3, 2018 at 19:53

answered Feb 3, 2018 at 19:47

Ansgar Wiechers

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