CODEWITHSUNDEEP
powershell
Andy
Andy

Reputation: 929

Adding members to PSCustomObject variable - understanding what's going on

I am trying to get my head around what is going on here, and I was wondering if anyone knew of a resource that might point me in the right direction, or could explain it a bit for me.

I am trying to create a PSCustomObject variable, and then members to it, like this:

$myObject += [PSCustomObject]@{
    FirstName = 'Bill'
    LastName = 'Bobbins'
    Age    = '30'
}

$myObject += [PSCustomObject]@{
    FirstName = 'Ben'
    LastName = 'Bobbins'
    Age    = '40'
}

So the first bit of code executes fine, but the second bit results in an error "Method invocation failed because [System.Management.Automation.PSObject] does not contain a method named 'op_Addition'." Also, if I pipe $myObject to get-member, I can see that $myObject is TypeName: System.Management.Automation.PSCustomObject.

Now, if I set $myObject to be an empty array first, and then try to add members, I am successful. This code works without error:

$myObject=@()

$myObject += [PSCustomObject]@{
    FirstName = 'Bill'
    LastName = 'Bobbins'
    Age    = '30'
}

$myObject += [PSCustomObject]@{
    FirstName = 'Ben'
    LastName = 'Bobbins'
    Age    = '40'
}

If I now pipe $myObject to get-member, I still get TypeName: System.Management.Automation.PSCustomObject. So my question is, why am I allowed to add multiple members to $myObject in the second example, but not in the first, when the data type is the same for both examples?

Any help is muchly appreciated!

Thanks

Upvotes: 2

Views: 1260

Answers (1)

G42
G42

Reputation: 10019

The issue here is with how Get-Member/the pipeline works - it's tripped me up before!

This will unroll the array, and give you the type of each element as it passes it across the pipeline:

$myObject | Get-Member

This will pass the whole object, and correctly give you the type as System.Object[]

 Get-Member -InputObject $myObject

You can test this out by for example adding $myObject += "test string" to the end of your code and trying to get members both ways. The first will return both PSObject and String types.

Sidepoint: The $myObject = @() line can be avoided by specifying you are creating an array the first time you declare $myObject. Example:

[array]$myObject = [PSCustomObject]@{

[PSCustomObject[]]$myObject = [PSCustomObject]@{

Upvotes: 3

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