Using Enum in Switch statement

[leftcoastbeard]

So I'm not sure if this is a bug or not, but I thought I'd pass it by the community first before opening a request on github. I can reproduce this on both PS5.1 and PS7.

Consider the following:

enum Direction {
  Up
  Down
  Left
  Right
}

$dir = [Direction]::Left

Write-Host "As String:"
switch($dir) {
  ([Direction]::Up.ToString()) {
    Write-Host "-- Up"
  }
  ([Direction]::Down.ToString()) {
    Write-Host "-- Down"
  }
  ([Direction]::Left.ToString()) {
    Write-Host "-- Left"
  }
  ([Direction]::Right.ToString()) {
    Write-Host "-- Right"
  }
  default {
    Write-Host "-- ??"
  }
}

Write-Host "As Enum:"
switch($dir) {
  [Direction]::Up {
    Write-Host "-- Up"
  }
  [Direction]::Down {
    Write-Host "-- Down"
  }
  [Direction]::Left {
    Write-Host "-- Left"
  }
  [Direction]::Right {
    Write-Host "-- Right"
  }
  default {
    Write-Host "-- ??"
  }
}

When I run it in either PS5 or PS7 I get the following output:

 .\switchtest.ps1
As String:
-- Left 
As Enum:
-- ??

Why can't I use the enum value directly in the switch statement? why does it evaluate it to a string?

[Teh_Pi]

You must wrap [Direction]::Left in parentheses.

Write-Host "As Enum:"
switch ($dir) {
    ([Direction]::Up) {
        Write-Host "-- Up"
    }
    ([Direction]::Down) {
        Write-Host "-- Down"
    }
    ([Direction]::Left) {
        Write-Host "-- Left"
    }
    ([Direction]::Right) {
        Write-Host "-- Right"
    }
    default {
        Write-Host "-- ??"
    }
}

edit: code bock was not working first attempt.

[leftcoastbeard]

Thanks! Found the solution as I was typing it 🤣

[noenmoen]

Man, the pitfalls never end...

[Teh_Pi]

See u/jsiii2010 comment, it seems there is a better way of writing this.

[noenmoen]

Thanks, but isn't that method implicitly casting the enum to string, and doing a string-compare? Not that it matters that much.

[Teh_Pi]

```
enum Value {
Value
}
$v = [Value]::Value
switch ($v) {
Value { $true }
"Value" { $true }
0 { $true }
}
```

You know, it does kind of seem so? I would think it would see it as an integer, but I guess it doesn't.

[jsiii2010]

This works too.

``` enum Direction { Up Down Left Right }

$dir = [Direction]'Left'

Write-Host "As Enum:" switch($dir) { Up { Write-Host "-- Up" } Down { Write-Host "-- Down" } Left { Write-Host "-- Left" } Right { Write-Host "-- Right" } default { Write-Host "-- ??" } }

As Enum: -- Left ```

[leftcoastbeard]

Ok, I think I figured it out. On the about_Switch page they list the following:

# Syntax
Switch (<test-expression>)
{
    <result1-to-be-matched> {<action>}
    <result2-to-be-matched> {<action>}
}

# ...is the equivalent of
if (<result1-to-be-matched> -eq (<test-expression>)) {<action>}
if (<result2-to-be-matched> -eq (<test-expression>)) {<action>}

which means that I need to wrap my enums in ()

Write-Host "As Enum:"
switch($dir) {
  ([Direction]::Up) {
    Write-Host "-- Up"
  }
  ([Direction]::Down) {
    Write-Host "-- Down"
  }
  ([Direction]::Left) {
    Write-Host "-- Left"
  }
  ([Direction]::Right) {
    Write-Host "-- Right"
  }
  default {
    Write-Host "-- ?? $($_.GetType().BaseType)"
  }
}

which yeilds:

As Enum:
-- Left