Powershell: Child Property Deflation - powershell

Question

Not sure if "deflating" is the right term, but I was wondering if there's a nicer way to specify that you only want to return a selection of an object's children's properties whilst using Select-Object? I'm using Powershell v5.
Here's a fully working example - the $test variable is hard coded here for demonstration purposes; in my use-case, the $test array is being returned from an API. I want to remove the name property from the testChild object during the projection.
The only way I could figure out how to do this is by using a foreach loop whilst piping into $result, then re-creating each child object and setting only the required properties, but it feels like powershell should have nicer way to do this.
$test = #(
[PSCustomObject]#{
testProp = "test1"
testChild = [PSCustomObject]#{
id = 1
name = "test name 1"
}
},
[PSCustomObject]#{
testProp = "test2"
testChild = [PSCustomObject]#{
id = 2
name = "test name 2"
}
}
)
$result = $test | select testProp, testChild | % {
$_.testChild = [PSCustomObject]#{
id = $_.testChild.id
}
$_
}
$result
This outputs:
testProp testChild
-------- ---------
test1 #{id=1}
test2 #{id=2}
Which is exactly what I want. I'd be nice if I could do something like this:
$result = $test | select testProp, testChild.id
Bearing in mind that I do not want flat properties returned - I want the original object with some properties removed / only the properties I specify included.

Answer 1

You can do this with Select-Object:
$result = $test | select testProp, #{
Name = 'id'
Expression = { $_.testChild.id }
}
Basically, Select-Object allows you to define your own properties, where the value is determined by an expression (a [ScriptBlock]), so you can run any code you want to determine the value. Within the block, $_ refers to the "current object" the same way it would in a ForEach-Object call.