Determine depth of object &/or JSON values using PowerShell Loop

Question

I am using an api to gather a list of comments for particular tickets, the tickets have nested comments which are returned from the api like so:

{
  "comments": [
    {
      "text": "test 1",
      "comments": [
        {
          "text": "test 2",
          "comments": [
            {
                "text": "test 3",
                "comments":[]
            }
          ]
        }
      ]
    }
  ]
}

The number of child comments can be n for any parent comment. I'm ultimately trying to get the text value for each "comments" tag until the "comments" tag is null.

I thought about making a parent object then trying to append the property search until it returns null.

 $n = 1

$exists = $true

while ($exists){ 
           
    $string = ".comments"     
    $search = $string * $n
    $search = $search.Substring(1)

    $m = $i.$search

    $commentVal = $m.comments
    $textValue = $m.text

    $textValue

    if ($textValue -ne ''){
        $comments +=  $textValue
    }
    
    if ($commentVal){            
        $exists = $true
    }else{           
        $exists = $false
    }
    $n++    
} 

This does work but only for one iteration. i.e. if $search = "comments.comments" $i.$search does not work, but $search = "comments"; $i.$search does work.

question from:https://stackoverflow.com/questions/65894693/determine-depth-of-object-or-json-values-using-powershell-loop

Answer 1

Here's a solution for you that converts the response to an object and recurses on the comments property:

$rawJson = @'
{
"comments": [
    {
    "text": "test 1",
    "comments": [
        {
        "text": "test 2",
        "comments": [
            {
                "text": "test 3",
                "comments":[]
            }
        ]
        }
    ]
    }
]
}
'@

$jsonObj = $rawJson | ConvertFrom-Json
$comment = $jsonObj.Comments
$allComments = while ($null -ne $comment) {
    $comment.text
    $comment = $comment.Comments
}

---

Edit
(a bit of explanation might be helpful)

if $search = "comments.comments" $i.$search does not work, but $search = "comments"; $i.$search does work.

This is expected, if not intuitive. $i.comments tells PowerShell to index on the comments property, and $i.comments.comments tells it to do twice.

Problem is when using a variable like in the case $search = "comments.comments", $search is not expanded; PowerShell will look for the literal property comments.comments.

Try your code on this json:

{
    "comments": [
        {
        "text": "test 1",
        "comments": [
            {
            "text": "test 2",
            "comments": [
                {
                    "text": "test 3",
                    "comments":[]
                }
            ]
            }
        ]
        }
    ],
    "comments.comments": [
        {
            "text": "test 2.0",
            "comments": [
                {
                    "text": "i'm not empty"
                }
            ]
        }
    ],
    "comments.comments.comments": [
        {
            "text": "test 3.0",
            "comments": [
                {
                    "text": "i'm not empty"
                }
            ]
        }
    ]
}