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Theunis
Theunis

Reputation: 75

Powershell: Referencing a single element in an Array

I would like to reference a single element inside an array, using the [ref] keyword.

How to test for a reference:

$var1 = "this is a string"
[ref]$var2 = [ref]$var1

$var2.Value
this is a string

$var2.Value += " too!"
$var2.Value
this is a string too!

$var1
this is a string too!

The above is working as expected. But now to reference a single element inside any array?

$var3="string 1", "string 2", "string 3"
[ref]$var2=[ref]($var3[1])

$var2.Value
string 2

$var2.Value += " updated!"
$var2.Value
string 2 updated!

$var3[1]
string 2

I expected $var3[1] to return the same as the value of $var2.Value. What am I doing wrong?

Upvotes: 6

Views: 2955

Answers (1)

mklement0
mklement0

Reputation: 437833

In PowerShell, you cannot obtain a reference to individual elements of an array.

To gain write access to a specific element of an array, your only option is:

  • to use a reference to the array as a whole

  • and to reference the element of interest by index.

In other words:

Given $var3 = "string 1", "string 2", "string 3", the only way to modify the 2nd element of the array stored in $var3 is to use $var3[1] = ... (barring acrobatics via C# code compiled on demand).

As for what you tried:

[ref] $var2 = [ref] ($var3[1])

In PowerShell, if you get the value of $var3[1], it is invariably a copy of the data stored in $var3's 2nd element (which may be a copy of the actual data, if the element contains an instance of a value type, or a copy of the reference to the instance of a reference type, otherwise).

Casting that copy to [ref] is therefore invariably disassociated from the array element of origin.

Upvotes: 4

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