Json text replace in string array using PowerShell

Question

Objective: to change from "some" to "that" in string array in Json

Json:

{
  "resources": [
    {
      "name": "item1",
      "dependsOn": [
        "somevalue",
        "somevalue"
      ]
    },
    {
      "name": "item2",
      "dependsOn": [
        "somemorevalue",
        "someothervalue"
      ]
    },
    {
      "name": "item3",
      "dependsOn": [
        "somemorevalue",
        "someothervalue"
      ]
    }
  ]
}

PowerShell Code:

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

$t.resources | ForEach-Object {
    $_ = $_.dependsOn | ForEach-Object {
        $_ = $_ -replace "some", "that"
    }
}

$t.resources

OutPut: I am getting following output after running the code. Could you help me what I am missing here?

name  dependsOn
----  ---------
item1 {somevalue, somevalue}
item2 {somemorevalue, someothervalue}
item3 {somemorevalue, someothervalue}

Mathias R. Jessen · Accepted Answer · 2022-02-17 12:36:35Z

3

You never assign anything back to the dependsOn property, hence the lack of persistence.

Change the second statement to:

$t.resources | ForEach-Object {
    $_.dependsOn = @($_.dependsOn -replace "some", "that")
}

Note that -replace can be applied to multiple input strings, so the inner ForEach-Object statement is unnecessary.

answered Feb 17, 2022 at 12:36

Mathias R. Jessen

178k13 gold badges175 silver badges234 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Sanjeev Kumar Over a year ago

Thanks, it worked, I was trying the same with $_ =$_ -replace in the inner loop, but it wasn't working. Thanks Again.

Mathias R. Jessen Over a year ago

@SanjeevKumar $_ = $_ -replace ... only overwrites the contents of the $_ variable - it doesn't modify the object that was previously stored in it

Vesper · Accepted Answer · 2022-02-17 12:42:30Z

You can replace values in place within foreach-loop in Powershell, but for that you need to modify fields of $_ instead of directly assigning a value to $_. Therefore in order to replace your dependsOn stuff, you need to recreate a part or the entire object $t by first returning the changed strings, then assigning the returned array or object to exact part of a bigger structure. Like this:

$t.resources | ForEach-Object {
    $_.dependsOn = $_.dependsOn | ForEach-Object {
        $_ -replace "some", "that"
    }
}

$t.resources

Here, first you call a foreach loop on a nested object's dependsOn array, but instead of assigning the value, you return it as an item not passed to any assignment, this instead goes outside the loop forming the array output of the foreach block. Then you assign the altered output to the processed object's field, instead of modifying the temporary variable $_ you dereference it thus gaining access to the exact object being processed, and are able to replace the value for dependsOn array with altered data.

Collectives™ on Stack Overflow

Json text replace in string array using PowerShell

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related