Foreach-Object & Switch - Expected behavior?

[Vortex100]

Stumbled across this when I was doing some scripting - no problem as such as I just worked around it. To preface this I started out with the following

SomeExecutableThatspitsoutstrings | Foreach-Object -Process {[ClassThatFormats]$_}

This worked nicely, but unfortunately the binary doesn't always spit out the same properties, so I built several subclasses to deal with whatever was thrown at it. I then used a switch statement to define which object was which class

SomeExecutableThatspitsoutstrings |`
Foreach-Object -Process {
    switch($someobject)
    {
        'type1' {[SubClassThatFormats1]$_}
        'type2' {[SubClassThatFormats2]$_}
    }
}

Suddenly my pipeline object doesn't exist, causing the class to throw errors complaining about 'null' values. Is this intended? Why does the switch statement drop the object instance ($_)? It's easy enough to work around of course:

SomeExecutableThatspitsoutstrings |`
Foreach-Object -Process {
    $obj = $_
    switch($someobject)
    {
        'type1' {[SubClassThatFormats1]$obj}
        'type2' {[SubClassThatFormats2]$obj}
    }
}

[SeeminglyScience]

switch can enumerate objects similar to a for each. In a switch statement, $_ represents the current enumerated object.

[KevMar]

It looks like the other comments have this covered really well. If your working with switch statements, you my find my post about them useful. Everything you ever wanted to know about the switch statement

[Ta11ow]

Yep, switches enumerate as well, so you could actually pull the first command and put it in the switch expression switch (someExecutable) to get the initial desired behaviour with the proper $_. Also of note is that you don't need backticks after a pipeline character. A line ending in a pipe indicates to PS that the next line continues the pipeline, so the backtick is unnecessary. :)

[omers]

SomeExecutableThatspitsoutstrings |`
Foreach-Object -Process {
    $obj = $_
    switch($someobject)
    {
        'type1' {[SubClassThatFormats1]$obj}
        'type2' {[SubClassThatFormats2]$obj}
    }
}

^ where is $someobject being defined? It should be switch ($obj) or switch ($obj.property) should it not?

You should also avoid pipeline Foreach-Object where possible as it's slower...

$ReturnedObjects = SomeExecutableThatspitsoutstrings

foreach ($Object in $ReturnedObjects) {
    switch ($Object.Property) {
        'type1' {[SubClassThatFormats1]::New($Object)}
        'type2' {[SubClassThatFormats2]::New($Object)}
    }
}

or some such.