CODEWITHSUNDEEP
arrayspowershell
DarkLite1
DarkLite1

Reputation: 14765

Initiate an array from Select-Object

I'm trying to generate an output string like Item1, Item2, that is joined with a comma separator. We do this by initiating an empty array in the Select-Object -Property.

Check this code:

$Test =  @(
    [PSCustomObject]@{
        Name = 'Test'
    }
    [PSCustomObject]@{
        Name = 'Test2'
    }
) | Select-Object -Property @{N = 'Problem'; E = { @() } },
@{N = 'EmployeeType'; E = { $null } }, *

foreach ($R in $Test) {
    $R.Problem += 'Item1'
    $R.Problem += 'Item2'
}


$Test | Select-Object -Property @{Name = 'Problem'; Expression = { $_.Problem -join "; " } }, * -ExcludeProperty Problem | fl

Result:

Problem      : Item1Item2
Name         : Test

Problem      : Item1Item2
Name         : Test2

Why is the property Problem concatenated as a String and not as an Array? How can it be converted to an Array?

Upvotes: 1

Views: 1188

Answers (2)

js2010
js2010

Reputation: 27626

Unfortunately that way to make an empty array didn't work.

PS C:\users\js> $test[0].problem.gettype()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $test[0].problem.gettype()
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

PS C:\users\js> $test[0].problem -eq $null
True

By the way, using "+=" kills puppies.

Upvotes: 0

Theo
Theo

Reputation: 61263

To instantiate an empty array in the expression of the calculated property, @() is not enough, because PowerShell will flatten that and it will become $null.

Use ,@() instead

$Test =  @(
    [PSCustomObject]@{
        Name = 'Test'
    }
    [PSCustomObject]@{
        Name = 'Test2'
    }
) | Select-Object -Property @{N = 'Problem'; E = { ,@() } },
                            @{N = 'EmployeeType'; E = { $null } }, *

foreach ($R in $Test) {
    $R.Problem += 'Item1'
    $R.Problem += 'Item2'
}

$Test | Select-Object -Property @{Name = 'Problem'; Expression = { $_.Problem -join "; " } }, * -ExcludeProperty Problem | fl

Returns:

Problem      : Item1; Item2
EmployeeType : 
Name         : Test

Problem      : Item1; Item2
EmployeeType : 
Name         : Test2

Upvotes: 6

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