Append Members to an Array in JSON with PowerShell

Question

I need to use Powershell to insert data into a json file within an array. Here is the json original structure

{
"Array": [
    {
        "servername": "foo"
    },
    {
        "servername": "boo"
    }
    ]
}

Here is the new structure:

   {
    "Array": [
        {
            "servername": "Foo",
            "Disk": "100"
        },
        {
            "servername": "Boo",
            "Disk": "500"
        }
    ]
   }

Why does this not work?

$json = @"
{
    "Array": [
        {
            "servername": "Foo"
        },
        {
            "servername": "Boo"
        }
        ]
    }
"@

$jsonServerFoo=@"
    {
    "Disk": "100"
    }
"@

$jsonServerBoo=@"
    {
    "Disk": "500"
    }
"@

$jsonObj = $JSON | ConvertFrom-Json
$jsonServerFooObj = $jsonServerFoo | ConvertFrom-Json
$jsonServerBooObj = $jsonServerBoo | ConvertFrom-Json
$i = 1 
$jsonObj.Array | Foreach-object {
    if ( $i -eq 1 ) {
        $_ | Add-Member -MemberType NoteProperty -Name "Disk" -Value $jsonServerFooObj.Disk
        $i++
    }
    else {
        $_ | Add-Member -MemberType NoteProperty -Name "Disk" -Value $jsonServerBooObj.Disk
    }
}
$jsonObj
$jsonObj | ConvertTo-Json -Depth 100

I get the desired output

{
    "Array":  [
                  {
                      "servername":  "Foo",
                      "Disk":  "100"
                  },
                  {
                      "servername":  "Boo",
                      "Disk":  "500"
                  }
              ]
}

With PS6 there is a “-AsHastable” property of Convert-FromJson which fixes this historic oversight.. — user2864740
– user2864740, Commented Dec 20, 2019 at 19:17

codewario · Accepted Answer · 2019-12-20 19:37:30Z

Use Add-Member to add members to a PSCustomObject. ConvertFrom-Json returns a PSCustomObject, not a Hashtable.

$jsonObj | Add-Member -MemberType NoteProperty -MemberName MyPropertyName -Value "some value, doesn't have to be a string"

You don't have to work with the base $jsonObj either, you can also add members to nested members of $jsonObj as well. In your case, with the Array member:

$jsonObj.Array | Foreach-object {
  if( $i -eq 1 ) {
    $_ | Add-Member -MemberType NoteProperty -Name Disk -Value $jsonServerFooObj.Disk
    $i++
  } else {
    $_ | Add-Member -MemberType NoteProperty -Name Disk -Value $jsonServerBooObj.Disk
  }
}

You may also want to consider calling ConvertTo-Json -Depth 100 so you don't get the default object depth which is low, 3 I think.

As noted by @user2864740, in PowerShell 6 ConvertFrom-Json has the -AsHashtable parameter if you would rather work with a Hashtable than a PSCustomObject.

Collectives™ on Stack Overflow

Append Members to an Array in JSON with PowerShell

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related