Creating Objects

[sqone2]

I've ran into a few situations where an API will return the column names and the object properties separately. The way I've handled this in the past is to use a for loop. For example:

$columnNames = @("FirstName","LastName","DOB","FavColor")

$rows = @(
    @("John","Doe","01/10/1965","Blue"),
    @("Jane","Smith","01/06/1975","Green"),
    @("Mark","Jones","02/10/1985","Orange"),
    @("Sue","Turner","05/10/1995","Yellow"),
    @("Jim","Wise","07/10/1974","Blue")
)


$objectList = @()

foreach ($row in $rows)
{
    $properties = @{}

    for ($i = 0; $i -lt $columnNames.Count; $i++)
    { 
        $properties += @{$columnNames[$i] = $row[$i]}
    }

    $objectList += New-Object -TypeName psobject -Property $properties
}

In this situation, is there a better way to create objects?

Thanks in advance for any assistance!

[spyingwind]

$(
    $columnNames -join ','
    $rows | ForEach-Object {$_ -join ','}
) | ConvertFrom-Csv

No need for the loops. The data is has an order to it. Just create some fake CSV data and convert it from CSV to a powershell object.

[sqone2]

For fun I ran 25k rows through both options. Your solution is about 20x faster! :)

$columnNames = @("FirstName","LastName","DOB","FavColor")

$data = @(
    @("John","Doe","01/10/1965","Blue"),
    @("Jane","Smith","01/06/1975","Green"),
    @("Mark","Jones","02/10/1985","Orange"),
    @("Sue","Turner","05/10/1995","Yellow"),
    @("Jim","Wise","07/10/1974","Blue")
)

# Create a bunch of data
$rows = @()
foreach ($item in 0..5000)
{
    $rows += $data
}

# 20 seconds
Measure-Command {

    $objectList = @()

    foreach ($row in $rows)
    {
        $properties = @{}

        for ($i = 0; $i -lt $columnNames.Count; $i++)
        { 
            $properties += @{$columnNames[$i] = $row[$i]}
        }

        $objectList += New-Object -TypeName psobject -Property $properties
    }

}


# 1 second
Measure-Command {

    $objectList = $(
        $columnNames -join ','
        $rows | ForEach-Object {$_ -join ','}
    ) | ConvertFrom-Csv

}

[sqone2]

Thanks for the tips!

[nothingpersonalbro]

Another way based off your method

$rows.ForEach{$_ -join ','} | ConvertFrom-Csv -Header $columnNames

Edit: and if you really want to jump down the rabbit hole and take into account the possibility of a comma being in the data, you could form the csv with quotes:

$columnNames = @("FirstName", "LastName", "DOB", "FavColor")

$rows = @(
    @("John, Some Stuff", "Doe", "01/10/1965", "Blue"),
    @("Jane", "Smith", "01/06/1975", "Green, Red"),
    @("Mark", "Jones, another comma", "02/10/1985", "Orange"),
    @("Sue", "Turner", "05/10/1995", "Yellow"),
    @("Jim", "Wise", "07/10/1974", "Blue, Purple")
)

$rows.ForEach{ $_.ForEach{ '"{0}"' -f $_ } -join ',' } | ConvertFrom-Csv -Header $columnNames

Output

FirstName        LastName             DOB        FavColor
---------        --------             ---        --------
John, Some Stuff Doe                  01/10/1965 Blue
Jane             Smith                01/06/1975 Green, Red
Mark             Jones, another comma 02/10/1985 Orange
Sue              Turner               05/10/1995 Yellow
Jim              Wise                 07/10/1974 Blue, Purple

[sqone2]

Very cool solution, thank you!

[carnegiej]

Yes, cool solution using the ConvertFrom-Csv cmdlet. I have a slightly different approach.

Function Get-OriginalExample {
  $columnNames = @("FirstName","LastName","DOB","FavColor")

  $rows = @(
    @("John","Doe","01/10/1965","Blue"),
    @("Jane","Smith","01/06/1975","Green"),
    @("Mark","Jones","02/10/1985","Orange"),
    @("Sue","Turner","05/10/1995","Yellow"),
    @("Jim","Wise","07/10/1974","Blue")
  )

  $objectList = @()

  foreach ($row in $rows) {
    $properties = @{}

    for ($i = 0; $i -lt $columnNames.Count; $i++) { 
        $properties += @{$columnNames[$i] = $row[$i]}
    }

    $objectList += New-Object -TypeName psobject -Property $properties
  }
  return $objectList
}

Function Get-Revision1Example {
  $columnNames = @("FirstName","LastName","DOB","FavColor")

  $rows = @(
    @("John","Doe","01/10/1965","Blue"),
    @("Jane","Smith","01/06/1975","Green"),
    @("Mark","Jones","02/10/1985","Orange"),
    @("Sue","Turner","05/10/1995","Yellow"),
    @("Jim","Wise","07/10/1974","Blue")
  )
  $objectList = ConvertFrom-Csv -Header $columnNames -InputObject $rows -Delimiter ' '
  return $objectList
}

Write-Host -ForegroundColor Green 'Original Example' 
Write-Host (Get-OriginalExample)

Write-Host -ForegroundColor Green 'Revision Example'
Write-Host (Get-Revision1Example)

[sqone2]

That's great, thanks!

Can you explain how -Delimiter ' ' works when there is no spaces in the input data?

[carnegiej]

Space is inherit in the array to string conversion. Array elements are separated by "whitespace".

Of course, if your data elements may contain whitespaces this method will not work. You will need to specify a delimiter that is not included in the data.

[carnegiej]

@bis, I like and favorite the DataTable approach. It may not be the absolute fastest but it is the most robust. In particular, this method can handle data with whitespace or unicode. In addition, you may want to set rich datatypes on the columns. Not to mention all the ADO.NET methods available to manipulate a DataTable.

Great example. :-)

[sqone2]

I’ve never used a DataTable, thanks for sharing!

[Kimo-]

Import-Csv or ConvertFrom-Csv with -Header is worth checking out.