How to check if a row exist in an object array?

Question

I have an array

$a = (Invoke-RestMethod -Uri "...." -Method Get) | select X,Y,Z # Object[] Z has type of datetime

$a has X, Y, Z.

Now I need to check if a row is in $a

$x,$y,$z = ....
if ($a -contains $x,$y, $x) { ... } # doesn't work

How to do it?

Try piping the select to Get-Member to see what properties are available. — user4317867
– user4317867, Commented Oct 2, 2019 at 22:21
You'll have to share what the data is and what you expect as a return. — user4317867
– user4317867, Commented Oct 2, 2019 at 23:02

mklement0 · Accepted Answer · 2019-10-03 21:52:23Z

1

It sounds like you want to test array $a for containing an object that has a given set of property values ($x, $y, $z) for a given set of property names (.X, .Y, .Z):

$hasObjectWithValues = [bool] $(foreach ($o in $a) {
    if ($o.X -eq $x -and $o.Y -eq $y -and $o.Z -eq $z) {
      $true
      break
    }
  })

^{Note: The cleaner form [bool] $hasObjectWithValues = foreach ... should work, but, as of PowerShell Core 7.0.0-preview.4, doesn't, due to this bug}

As for what you tried:

$a -contains $x,$y, $z

The RHS of PowerShell's -contains operator only supports a scalar (single value), to be tested for equality with the elements in the the array-valued LHS.

However, even if you wrapped your RHS into a single object - [pscustomobject] @{ X = $x, Y = $y, Z = $z }, that approach wouldn't work, because [pscustomobject]s, as also returned by Invoke-RestMethod, are reference types, which - in the absence of custom equality comparison behavior - are compared by reference equality, meaning that they're only considered equal if they refer to the very same object in memory.

edited Oct 3, 2019 at 21:52

answered Oct 3, 2019 at 2:43

mklement0

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1 Comment

mklement0 Over a year ago

@ca9163d9: My bad - I forgot about this bug, which didn't surface in my informal tests. Please try my update.

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