Array Row index function

Question

I created a function to find an item in an array so I can update it.

  function Get-ArrayRowIndex {
                param(
                    [parameter(mandatory = $true)][array]$Property,
                    [parameter(mandatory = $true)][string]$Value
                )
           
                #Loop through array,incrementing index until value is found. Jordan wrote this and I refined it.
                [int]$index = 0
                while ($index -lt ($Property.count)) {
                    if ($Property[$index] -eq $Value) {
                        break
                    }
                    $index++
                }
                return [int]$index
            }

The problem is when the object is not found the function returns the total number of items in the array. How can I return an error if not found?

How about, after the loop, you test whether $index equals $Property.count and, if so, return an error? — adv12
– adv12, Commented Jan 5, 2022 at 22:01
Good pointer, @adv12, but the caveat is that with strings .IndexOf() is case-sensitive, whereas PowerShell's operators (such as -eq) are case-insensitive. — mklement0
– mklement0, Commented Jan 5, 2022 at 22:12
just for my curiosity ... what do you need the index of an array object for? i usually grab the object itself. the .Where({}) array method is both fast and rather flexible. — Lee_Dailey
– Lee_Dailey, Commented Jan 6, 2022 at 1:37
@dcaz - try taking a look at the speed [and simplicity] of using $Collection.Where({Filter code here}) gives you. it otta be faster than hunting down an index to use later for accessing the desired object from an array. — Lee_Dailey
– Lee_Dailey, Commented Jan 6, 2022 at 17:21

mklement0 · Accepted Answer · 2022-01-05 22:20:11Z

If you want to throw an error in case the value isn't found:

function Get-ArrayRowIndex {
                param(
                    [parameter(mandatory = $true)][array]$Property,
                    [parameter(mandatory = $true)][string]$Value
                )
           
                [int]$index = 0
                while ($index -lt ($Property.count)) {
                    if ($Property[$index] -eq $Value) {
                        # Found -> output the value and return (exit) here.
                        return $index 
                    }
                    $index++
                }
                # Getting here means that the value wasn't found.
                throw "'$Value' not found in the given array."
            }

Note that you could use the [Array]::FindIndex() method instead of looping through the array yourself:

# Returns the index if found; -1 otherwise.
[Array]::FindIndex(
  $Property, 
  [Predicate[object]] { $Value -eq $args[0] }
)

[Array].IndexOf() is another option, but only if case-sensitive string comparison is desired (whereas PowerShell's operators, such as -eq used above, are case-insensitive by default); e.g., ('FOO', 'bar').IndexOf('foo') yields -1 (not found) and ('FOO', 'foo').IndexOf('foo') yields 1

iRon · Accepted Answer · 2024-02-26 09:14:33Z

3

The PowerShell way, using Select-String:

$Properties = 'One', 'Two', 'Three'
$Value = 'Two'
($Properties | Select-String -SimpleMatch -Pattern $Value).LineNumber

2

Throwing errors:

$Found = $Properties | Select-String -SimpleMatch -Pattern $Value
Switch ($Found.Count) {
    0       { Throw "$Value not found" }
    1       { $Found.LineNumber }
    Default { Throw "More than one $Value found" }
}

edited Feb 26, 2024 at 9:14

answered Jan 6, 2022 at 8:17

iRon

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1 Comment

stansy Over a year ago

Great - good job!

Santiago Squarzon · Accepted Answer · 2024-02-26 12:32:46Z

3

Normally a for loop is a cleaner approach for this:

function Get-ArrayRowIndex {
    param(
        [Parameter(Mandatory)]
        [array] $Property,

        [Parameter(Mandatory)]
        [string] $Value
    )

    for ($i = 0; $i -lt $Property.Count; $i++) {
        if ($Property[$i] -eq $Value) {
            return $i
        }
    }

    throw "$Value not found in this array."
}

$arr = 0..10
Get-ArrayRowIndex $arr 4  # => returns 4
Get-ArrayRowIndex $arr 11 # => throws "11 not found in this array."

edited Feb 26, 2024 at 12:32

answered Jan 5, 2022 at 22:01

Santiago Squarzon

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