Updating variables within variables in Powershell

I don't know much about Powershell but I try to learn.
Can you help me to understand and solve what I want to do:

$string1=""

$complicatedString1 = "This is a complicated $string1"
$complicatedString2 = "$complicatedString1 too"

$string1 = "Test"

$complicatedString1 -> Should state now: This is a complicated Test
$complicatedString2 -> Should state now: This is a complicated Test too.

$string1 = "question"

$complicatedString1 -> Should state now: This is a complicated question
$complicatedString2 -> Should state now: This is a complicated question too.

and so on.

The idea sounds simple: I want to define strings that serve as templates, but with variable content.
In this case I want to manipulate $string1 and update $complicatedstring 1 and 2 so that any change of $string1 gets reflected in those strings.

$string1 would change frequently and at the moment I have no approach how get the changed values into those strings. Basically the're just placeholders to wait for being changed.

I'm not quite sure, but I think your question is about using template strings you can alter using new strings-to-insert.

The most elegant way to do that I think is by making use of the PowerShell -f format operator like this:

# the template strings
$complicatedString1 = "This is a complicated {0}"
$complicatedString2 = "{0} too"

# use the template strings to return new strings
$string1 = $complicatedString1 -f "Test"                # --> "This is a complicated Test"
$string2 = $complicatedString2 -f $string1              # --> "This is a complicated Test too"

$string1 = $complicatedString1 -f "question"            # --> "This is a complicated question"
$string2 = $complicatedString2 -f $string1              # --> "This is a complicated question too"

You can also use the Format method of the string object itself if you like:

$string1 = [string]::Format($complicatedString1, "Test")
$string2 = [string]::Format($complicatedString2, $string1)

which will give you the exact same results

• PowerShell -f operator
• String.Format

For this you need to put you complicatedString1 and complicatedString2 in single quotes (otherwise they will be directly expanded), than you might use the $ExecutionContext.InvokeCommand.ExpandString method:

$complicatedString1 = 'This is a complicated $string1'
$complicatedString2 = '$complicatedString1 too'

$string1 = 'Test'

$ExecutionContext.InvokeCommand.ExpandString($complicatedString1)
This is a complicated Test
$ExecutionContext.InvokeCommand.ExpandString($ExecutionContext.InvokeCommand.ExpandString($complicatedString2))
This is a complicated Test too

$string1 = "question"

$ExecutionContext.InvokeCommand.ExpandString($complicatedString1)
This is a complicated question
$ExecutionContext.InvokeCommand.ExpandString($ExecutionContext.InvokeCommand.ExpandString($complicatedString2))
This is a complicated question too

Note that you will need to use the ExpandString method twice on the $complicatedString2 to get to the bottom of the $string1 expansion.

To get a better overview, you might consider to create a recursive function with a -Depth parameter:

Function Expand([String]$String, [Int]$Depth = 1) {
	$Expand = $ExecutionContext.InvokeCommand.ExpandString($String)
	If ($Depth-- -ge 0) {Expand $Expand $Depth} Else {$Expand}
}

$string1 = 'Test'

Expand $complicatedString1
This is a complicated Test
Expand $complicatedString2 -Depth 2
This is a complicated Test too

You can also do it via a loop

do {
    $string1 = Read-Host "Please enter a word"
    $complicatedString1 = "This is a complicated $string1"; $complicatedString1
    $complicatedString2 = "$complicatedString1 too`n"; $complicatedString2
} while ($string1 -ne "exit program")

Output

Please enter a word: Test
This is a complicated Test
This is a complicated Test too

Please enter a word: Question
This is a complicated Question
This is a complicated Question too

Please enter a word: Exit Program
This is a complicated Exit Program
This is a complicated Exit Program too
#Program Exits#