Accessing an pscustomobject with dot notation in a string

Question

Given this piece of code

$Object = @"
{
    "Item1":{
        "Subitem1":{
            "Subsubvalue":"Value"
        }
    },
    "Value1":"value1"
}

"@ | ConvertFrom-Json

and given the following string (that I don't know at runtime, I've just got a string with an object path)

$String = "$Object.Item1.Subitem1.Subsubvalue"

I am trying to do the following - but I can't find a way to make it work

PS C:\> $Substring = $string.substring(8)
PS C:\> $Object.$Substring 
Value

My ultimate goal is to get to modify the contents of that

PS C:\> $Object.$Substring = "something else"

Obviously $substring approach doesn't work, nor the other approaches I've tried.

For me, its not clear what you want to achive. There are multiple outcomes that I can imagine with multiple ways to do it. — restless1987
– restless1987, Commented May 15, 2017 at 13:06

Chris Gardner · Accepted Answer · 2017-05-15 13:04:26Z

2

You can use Invoke-expression to handle this as it will parse the string passed to it as if it was a command.

So you can do the following:

Invoke-Expression -Command "$string"

This will return:

Value

So you can then do:

Invoke-Expression -Command "$String = `"Something else`""

Which will set the value to "Something else".

answered May 15, 2017 at 13:04

Chris Gardner

712 bronze badges

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

Comments

Ansgar Wiechers · Accepted Answer · 2017-05-15 15:55:24Z

1

Invoke-Expression is no better than eval in other languages. It's far too likely to do something undesired/unexpected because it evaluates the given string as code. I would not recommend going that route unless you know exactly what you're doing.

Try a recursive function instead:

function Get-NestedItem {
    Param(
        [Parameter(Mandatory=$true, Position=0)]
        $InputObject,

        [Parameter(Mandatory=$false, Position=1)]
        [AllowEmptyString()]
        [string]$Path = '',

        [Parameter(Mandatory=$false, Position=2)]
        [string]$Delimiter = '.'
    )

    if ($Path) {
        $child, $rest = $Path.Split($Delimiter, 2)
        Get-NestedItem $InputObject.$child $rest
    } else {
        $InputObject
    }
}

$Object = ...
$Path   = 'Item1.Subitem1.Subsubvalue'

Get-NestedItem $Object $Path

answered May 15, 2017 at 15:55

Ansgar Wiechers

202k27 gold badges286 silver badges363 bronze badges

1 Comment

Michael B Over a year ago

That's an interesting approach! I'll try it out. (and I see your point about the security risk too)

Negatar · Accepted Answer · 2018-09-04 23:47:45Z

0

You might also consider using a dedicated function to do this work rather than depending on Invoke-Expression. Solutions like this are detailed in this tread.

answered Sep 4, 2018 at 23:47

Negatar

8091 gold badge10 silver badges15 bronze badges

Collectives™ on Stack Overflow

Accessing an pscustomobject with dot notation in a string

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related