在 PowerShell 中更改 function 中变量的声明数据类型

Question

I have a PowerShell script where I want to declare a variable data type at the beginning, and there is a function that changes this data type on certain conditions. I can make it work if this is done outside of the function, but I can't change the data type inside the function, even though I use scope modifiers.

If I put this in script foobar:

[string]$foo = "123"
[int]$foo = $foo
$foo.GetType()

And execute the script:

PS C:\> .\foobar.ps1

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Int32                                    System.ValueType

But if I put this:

[string]$foo = "123"
Function bar {
    [int]$script:foo = $foo
    $foo.GetType()
}
bar

And I execute:

PS C:\> .\bar.ps1

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String                                   System.Object

The important note here is that the second scenario only happens if you execute the code from a script. The result will be different when executing directly from terminal. I want the data type to change to integer on both scenarios. Any ideas?

Answer 1

Pass in reference variables like below

[string]$foo = "123"

Function bar([ref]$foo) {
[int]($foo)  ='123'
    
 ##  Get-Variable -Name foo -Scope global | select fullname
$foo.GetType()
 }

Answer 2

You can specify what that output object would be with [OutputType()]

[string]$foo = "123"
Function bar {
    [OutputType([int])]
    [int]$script:foo = $foo
    $foo.GetType()
}
bar

You can read more about it here outputType