How to get index of hashtable in array?

Question

I'm having a little trouble finding the index of a hashtable in an array. I create a JSON with this code:

$start = {
Clear-Host
$BIB = Read-Host 'Bibliothek'
$BIBName = Read-Host 'Bibliothek Name'
$Standort = Read-Host 'Bibliothek Standort'
$Autor = Read-Host 'Buchautor'
$BuchName = Read-Host 'Buchname'

$jsonfile = "C:\Skripte\bibV2-1000.xml"
if(![System.IO.File]::Exists($jsonfile)){
    $Data = @{BIBs = @(
        @{$BIB = @{BIBName=$BIBName}, 
        @{Standort = $Standort}, 
        @{Bücher = @(
            @{BuchName = $BuchName; 
            Autor = $Autor})
        }}
    )}
    ConvertTo-Json -Depth 50 -InputObject $Data | Add-Content $jsonfile
    .$continue
} else {
        $jsonfile = "C:\Skripte\bibV2-1000.json"
        $Data = Get-Content $jsonfile | ConvertFrom-Json
        $Data.BIBs += New-Object -TypeName psobject -Property @{$BIB = 
               @{BIBname=$BIBName},
               @{Standort=$Standort},
               @{Bücher = @(@{
                    Buchname=$BuchName;
                    Autor=$Autor})
               }
        }
        ConvertTo-Json -Depth 50 -InputObject $Data | Out-File $jsonfile}
        .$continue
}


$continue = {
Write-Host ""
Write-Host "Was wollen Sie machen?"
Write-Host "(1) Eine weitere Bibliothek hinzufügen"
Write-Host "(2) Einer Bibliothek neue Bücher hinzufügen"
Write-Host "(E) Script beenden"

    If (($read = Read-Host ) -eq "1") {
    &$start} else {
            if (($read) -eq "2") {
                . C:\Skripte\büc.ps1 } else {
                    if (($read) -eq "E") {
                        exit} else {
                            Write-Host "+++ FALSCHE EINGABE! Bitte wählen Sie (1) oder (2) für die entsprechende Aktion +++"
                            .$continue
                        }
                }
    }
}
&$start

The output is as follows:

{
    "BIBs": [{
        "BIB1": [{
            "BIBName": "123"
        },
            {
                "Standort": "123"
            },
            {
                "Bücher": [{
                    "Autor": "123",
                    "BuchName": "123"
                }]
            }
        ]
    },
        {
            "BIB2": [{
                "BIBname": "345"
            },
                {
                    "Standort": "345"
                },
                {
                    "Bücher": [{
                        "Autor": "345",
                        "Buchname": "345"
                    }]
                }
            ]
        }
    ]
}

Now I want to find out the index of "BIB1". I already tried the IndexOf()-Method which should create the output "0" but it gives me "-1" instead, because it can't find the value. How can I get the index of "BIB1"?

Answer 1

^{Judging by your earlier question , you're attempting to get the index of a specific object so you can access it via its containing array. However, you can do this more directly: $objOfInterest = $Data.BIBs | ? BIB1 $objOfInterest = $Data.BIBs | ? BIB1 $objOfInterest = $Data.BIBs | ? BIB1 - see my answer to your earlier question for details.}

You need to iterate over the array elements of $Data.BIBs , which - on reading your serialized-to-a-file-as-JSON hashtables back in with ConvertFrom-Json - are custom objects (as Ansgar correctly points out; they are instances of [System.Management.Automation.PSCustomObject] ), and check each for the presence of property 'BIB1' :

• (In a hashtable, you'd check for the presence of key 'BIB1' with .ContainsKey('BIB1') )

• To test the existence of an object property , you need reflection , which is most easily - but somewhat obscurely - achieved via the hidden .PSObject property, as demonstrated in Ansgar Wiechers' more elegant solution .

However, given that the properties of interest have nonempty values, we can infer from the presence of a nonempty value that a given property exists, using implicit Boolean (logic): $obj.'BIB1' by default returns $null if there is no BIB1 property, which is "falsy" in a Boolean context such as an if conditional; conversely, any nonempty value is "truthy":

$propName = 'BIB1'
$i = $ndx = -1
foreach ($obj in $Data.BIBs) {
  ++$i
  if ($obj.$propName) { $ndx = $i; break}
}
$ndx  # $ndx now contains the index of the target object or -1 if there was no match

Answer 2

$Date.BIBs is an array of custom objects, not hashtables (since you wrote your original data to a JSON file and then converted that back), so you need something like this:

$arr = $Data.BIBs | ForEach-Object { $_.PSObject.Properties.Name }
$arr.IndexOf('BIB1')  # returns 0
$arr.IndexOf('BIB2')  # returns 1