Find duplicates in array of hashtables

Question

I have an array of hashtables and I need to find if there are elements who has the same Name.

I have this HasDuplicate function which return True or False if the array contains duplicate or not.

What I am doing here is that I am iterating through each element and add Name of it to another array, and then check it if it exists. But this code does not looks good, and I was thinking if there is another way of achieving this

# object looks like this
$array = @(
    @{ Name = 'First', Passed = $True }
    @{ Name = 'First', Passed = $False }
)

Function HasDuplicate
{
    param($array)
    $all = @()
    foreach($item in $array)
    {
        $item_name = $item.Name
        if($all -contains $item_name)
        {
            Write-Error "Duplicate name ""$item_name"""
            return $True
        }
        else
        {
            $all += $item_name
        }
    }
    return $False
}

Please define "good looking"

P-L
– P-L

2019-10-09 13:48:38 +00:00
Commented Oct 9, 2019 at 13:48 — P-L
– P-L, Commented Oct 9, 2019 at 13:48

Dave Sexton · Accepted Answer · 2019-10-09 13:51:09Z

8

Group-Object is probably the easiet, something like this:

$array = @(
    @{ Name = 'First'; Passed = $True }
    @{ Name = 'First'; Passed = $False }
)

$array.Name | Group-Object | Where-Object Count -GT 1

edited Oct 9, 2019 at 13:51

answered Oct 9, 2019 at 13:47

Dave Sexton

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1 Comment

P-L Over a year ago

I think you mean -GT 1

Dave Sexton · Accepted Answer · 2019-10-09 14:02:47Z

0

Another way you could do it using an hash table:

$array = @(
    @{ Name = 'First'; Passed = $True }
    @{ Name = 'First'; Passed = $False }
)


$h = @{}
$array | % {$h[$_.Name] += 1 }
$h.GetEnumerator() | Where value -GT 1

answered Oct 9, 2019 at 14:02

Dave Sexton

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Comments

RoadRunner · Accepted Answer · 2019-10-10 05:43:45Z

0

This might not be very good looking compared to the other answers, but you could just count your names in another hashtable then output the duplicates afterwards.

$array = @(
    @{ Name = 'First'; Passed = $True }
    @{ Name = 'First'; Passed = $False }
);

# Count names in array
$counts = @{}
foreach ($object in $array) {
    $name = $object.Name
    if (-not $counts.ContainsKey($name)) {
        $counts[$name] = 0
    }
    $counts[$name] += 1
}

# Output duplicates
foreach ($name in $counts.Keys) {
    if ($counts[$name] -gt 1) {
        Write-Output ("Duplicate Name: " + $name)
    }
}

Output:

Duplicate Name: First

answered Oct 10, 2019 at 5:43

RoadRunner

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