How to get child object from PSObject using dot notation string - powershell

Question

providing I have the following JSON
{
"firstName": "Frank",
"lastName": "Smith",
"age": "25",
"address": {
"streetAddress": "21 3rd st",
"city": "New York",
"state": "NY",
"postalCode": "10021"
},
"phoneNumber": [
{
"type": "home",
"number": "212 555-1234"
},
{
"type": "fax",
"number": "646 555-4567"
}
]
}
I need to be able to update a value using dotted notation.
$path = "C:\somePath\test.json"
$node = "address.streetAddress" # should also work with "phoneNumber[0].number"
$value = "21 Jump St."
$config = Get-Content -Path $path -Raw | ConvertFrom-Json
$config.$node = $value
Write-Host $config.$node
#Set-Content $path $($config | ConvertTo-Json)
The problem I'm getting is that the property cannot be found.
Exception setting "address.streetAddress": "The property 'address.streetAddress' cannot be found on this object. Verify that the property exists and can be set."
What do I need to do to be able to pass in dotted notation, and update the appropriate value?

Answer 1

While you can put a single property name in a variable and use that to access the property, you can't do that for multiple, dotted properties. You can work around this by using Invoke-Expression:
Invoke-Expression "`$config.$node = `$value"

Answer 2

Shortest way around it is:
$config.$($node) = $value
Level of nesting does not matter, You can do this:
$config.$($node).$($subnode).$($subSubNode) = $value
You can also refer to properties in objects like this:
$config.$($node.nodename)=$value