"Everything you ever wanted to know about the switch statement" – Missing example for switching on types

[SetTrend]

Type of issue

Missing information

Feedback

It seems hard to create a switch on types.

The following doesn't work:

$var = @{A = $true; B = 'abc'}

foreach ($key in $var.Keys)
{
  switch ($var[$key].GetType())
  {
    [bool] { if ($var[$key]) { $key } }
    [string] { "$key: $($var[$key])" }
  }
}

May I suggest to add information for this case to the below mentioned documentation page?

Page URL

https://learn.microsoft.com/en-us/powershell/scripting/learn/deep-dives/everything-about-switch?view=powershell-7.4

Content source URL

https://github.com/MicrosoftDocs/PowerShell-Docs/blob/main/reference/docs-conceptual/learn/deep-dives/everything-about-switch.md

Author

@sdwheeler

Document Id

9c03bc13-a80c-0a4c-0537-81235d4a849c

[sdwheeler]

The type is being parsed as a typecast on the scriptblock. Enclose the matching condition in a script block to avoid the typecast.

switch ($var[$key].GetType())
{
    {$_ -eq [bool]} { if ($var[$key]) { $key } }
    {$_ -eq [string]} { "$key`: $($var[$key])" }
}

[SetTrend]

Thanks for clarifying, @sdwheeler!

Coincidentally, I just found another GitHub issue, proposing an improvement to the PowerShell language: PowerShell/PowerShell#17456

It claims that it's sufficient to surround the type declaration with parentheses:

switch ($var[$key].GetType())
{
  {[bool]} { if ($var[$key]) { $key } }
  {[string]} { "$key`: $($var[$key])" }
}

I just tested it, and it works.

Perhaps the documentation may give some kind of rule or explanation on when and why parentheses are required in a switch statement condition.

It looks like omitting the parentheses is more or less some kind of special case?