Variables in command when calling hashtable

Question

I'm trying to fetch a value from a hashtable like the one below.

$Hashtable1AuthTestID = @{ 
    "BID_XPI" = "(id 2)";
    "MBID_XPI" = "(id 3)";
    "T_XPI" = "(id 4)";
    "ST_XPI" = "(id 5)";
    "SI_XPI" = "(id 6)";
    "T_SAML" = "(id 7)";
    "ST_SAML" = "(id 8)";
    "SI_SAML" = "(id 9)";
    "BID_SAML" = "(id 10)";
    "MBID_SAML" = "(id 11)";
}

It's working fine if I use $Hashtable1AuthTestID.BID_XPI but since this will be a generic script for several different type of data (and environments) I would like to include several variable when I call the hashtable such as the one below.

# Without variables (Example): $Hashtable1AuthTestID.BID_XPI 
# With variables (Example): $<Hashtable><Type><Environment>.<Method>

$hashtable = "Hashtable1"
$type = "Auth"
$environment = "Test"
$method = "BID_XPI"
# ID is the example is a string.

$'$hashtable1'$environment"ID".$method
$$hashtable1$environment+"ID".$method

I've tested several different approaches but can't get it working. I do get the correct syntax (if I print the values from the variables) such as $Hashtable1AuthTestID.BID_XPI but I don't get the actual value from the hashtable ((id 2)).

You have duplicated S_XPI key in your example hashtable, might want to correct that. — Robert Dyjas
– Robert Dyjas, Commented Jun 17, 2019 at 7:49
The $environment = "Test" is missing ID. If you build the string with those variables you get $Hashtable1AuthTest.BID_XPI not $Hashtable1AuthTestID.BID_XPI — T-Me
– T-Me, Commented Jun 17, 2019 at 8:04

Ansgar Wiechers · Accepted Answer · 2019-06-17 08:09:52Z

Referencing individually named variables by using a name from another variable -although possible- is a misguided approach. Don't do it. The canonical way of dealing with situations like this is to use either an array, if you want to access the data structure or object by index:

$hashtables = @()
$hashtables += @{
    "BID_XPI"  = "(id 2)"
    "MBID_XPI" = "(id 3)"
    ...
}

$hashtables[0].MBID_XPI

or a hashtable, if you want to access the data structure or object by name:

$hashtables = @{}
$hashtables['Hashtable1AuthTestID'] = @{
    "BID_XPI"  = "(id 2)"
    "MBID_XPI" = "(id 3)"
    ...
}

$hashtable   = 'Hashtable1'
$type        = 'Auth'
$environment = 'Test'
$method      = 'BID_XPI'

$name = "${hashtable}${type}${environment}ID"

$hashtables.$name.$method

For the sake of completeness, here is how you would get a variable by using a name from another variable, but again, this is NOT RECOMMENDED.

$Hashtable1AuthTestID = @{
    "BID_XPI"  = "(id 2)"
    "MBID_XPI" = "(id 3)"
    ...
}

$hashtable   = 'Hashtable1'
$type        = 'Auth'
$environment = 'Test'
$method      = 'BID_XPI'

$name = "${hashtable}${type}${environment}ID"

(Get-Variable -Name $name -ValueOnly).$method

mhu · Accepted Answer · 2019-06-17 08:03:50Z

0

You could use Get-Variable:

$hashtable = "Hashtable1"
$type = "Auth"
$environment = "Test"
$method = "BID_XPI"

(Get-Variable -Name "$($hashtable)$($type)$($environment)ID".).Value.$method

answered Jun 17, 2019 at 8:03

mhu

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Comments

T-Me · Accepted Answer · 2019-06-17 08:18:35Z

0

If you are able to print it you can invoke it:

$string = '${0}{1}{2}ID.{3}' -f $hashtable,$type,$environment,$method
Invoke-Expression -Command $string

answered Jun 17, 2019 at 8:18

T-Me

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1 Comment

Ansgar Wiechers Over a year ago

DO NOT use Invoke-Expression.

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