Object variable changes to a string

Question

I have a variable set as an object as follows:

[object] $x = 'abc','def';

If I view what $x is now, I get:

acb
def

Now my problem is when I set $x to $null and then try to rather set $x from a loop using += after reading the file it change $x type to a string and if I view what $x is now it gives me:

abcdef

instead of:

abc
def

How do I go about it to keep the variable as an object rather then a string?

Below is just a sample to get the idea:

[object] $x = 'abc','def';

$x = $null;

for ($i = 0; $i -lt $numberOfColumns; $i++) {
  $x += '$_.' + $NamesOfColumns[$i] + '.Trim()';
}

Thank you for responding. It worked in keeping it as an object but dynamically it still sees the object somehow different from when you type it in. wait.. to finish comment still typing — Costa Zachariou
– Costa Zachariou, Commented Aug 13, 2016 at 11:54
I believe I told you this before, but the approach you're taking (building and invoking command strings) is unnecessarily complicated and convoluted. Your time would be far better spent adjusting your code to what I posted in response to your last question instead of working around all the pitfalls and issues that will inevitably pop up if you continue this route. — Ansgar Wiechers
– Ansgar Wiechers, Commented Aug 13, 2016 at 13:33

PatM0 · Accepted Answer · 2016-08-13 12:09:10Z

What you do within your code is:

[object] $x = 'abc', 'def'

==> The type of 'abc' and 'def' is [System.String]. Because you comma seperated them PowerShell does automatically create a list. So after executing that line $x is a System.Object[]. Index 0 and 1 contains [System.String].

$x = $null;

==> Now you define $null as the value for $x. So you are removing the value. The type of $x is now undefinded. You can set the value 123 then $x will become type System.Int32. You can redefine a string and so on.

Within your for-loop you use

$x += 'somestring' + $addingSomeStuff + 'otherstring'

==> The result here is that within the first Iteration of the for-loop PowerShell will assign a String to $x. So the type of $x will be [System.String]. In the next iterations the += operator adds additionally content to the value of $x, which is still [System.String]

Don't set $x to $null. Because you'll loose the type information. For more information read about the PowerShell Extended Type System.

The following snippet works. Hope that helps.

############################################
# The following was not part of your post  #
#    I added it to get it run in general   #
$numberOfColumns = 2
$NamesOfColumns = 'Column1', 'Column2'
############################################

[object] $x = 'abc','def';

# don't set $x to $null
# define an empty list instead ;-)
$x = @()

for ($i = 0; $i -lt $numberOfColumns; $i++) {
  $x += '$_.' + $NamesOfColumns[$i] + '.Trim()';
}

Community · Accepted Answer · 2017-05-23 12:15:00Z

In the underlying type system (.NET CTS), [object] is the base class for any object, and is the most vague type description you can give any variable - it doesn't convey any specialized meaning at all.

As mentioned in @PatM0's answer, the best solution here is to initialize the variable value with the array subexpression operator (@()) before using += :

$x = @()

If you really want to force a variable to be a collection type, use the array or psobject[] type accelerators:

PS C:\> [array]$x = 'abc','def'
PS C:\> $x = $null
PS C:\> $x += 'abc'
PS C:\> $x += 'def'
PS C:\> $x
abc
def
PS C:\> [psobject[]]$x = 'abc','def'
PS C:\> $x = $null
PS C:\> $x += 'abc'
PS C:\> $x += 'def'
PS C:\> $x
abc
def

Compare with [object]:

PS C:\> [object]$x = 'abc','def'
PS C:\> $x = $null
PS C:\> $x += 'abc'
PS C:\> $x += 'def'
PS C:\> $x
abcdef

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