How to return several items from a Powershell func

问题:

In a script I have several functions that need to break down an SVN external definition. These can either be <url> <path>, -r<rev> <url> <path>, or -r <rev> <url> <path>, and the mechanics I came up with to extract the data is more than just two lines, so I want to put this into a separate function.

But when I do so, I end up with three variables containing the relevant data which are local to the function, and I see no way to get all three of them them to the caller.

In a proper programming language I would return a compound type containing all three values, but I don't see how to do that in Powershell. Of course, I could split this into three separate functions, but then I am back at violating the DRY rule.

So what can I do here in Powershell?

回答1:

You can return an array of [string] and then let the caller split it or return a custom object and always the caller do the split.

回答2:

I agree with @Christian, and I add another solution.

First you can return using an array explicitly or implicitly :

A) explicitly

function ExplicitArray ()
{
  $myArray = @()

  $myArray += 12
  $myArray += "Blue"

  return ,$myArray
}

Clear-Host
$a = ExplicitArray
Write-Host "values from ExplicitArray are $($a[0]) and $($a[1])"

B) implicitly

function ImplicitArray ()
{
  Write-Output 12

  Write-Output "Blue"
  return "green"
}

$b = ImplicitArray
Write-Host "values from ImplicitArray are $($b[0]), $($b[1]) and $($b[2])"

Second you can return a custom object :

A) Short form

function ReturnObject ()
{
  $value = "" | Select-Object -Property number,color
  $value.Number = 12
  $value.color = "blue"
  return $value
}
$c = ReturnObject
Write-Host "values from ReturnObject are $($c.number) and $($c.color)"

B) School form

function SchoolReturnObject ()
{
  $value = New-Object PsObject -Property @{color="blue" ; number="12"}
  Add-Member -InputObject $value –MemberType NoteProperty –Name "Verb" –value "eat"
  return $value
}
$d = SchoolReturnObject
Write-Host "values from SchoolReturnObject are $($d.number), $($d.color) and $($d.Verb)"

Third using argumen by reference

function addition ([int]$x, [int]$y, [ref]$R)
{
 $Res = $x + $y
 $R.value = $Res
}

$O1 = 1
$O2 = 2
$O3 = 0
addition $O1 $O2 ([ref]$O3)
Write-Host "values from addition $o1 and $o2 is $o3"

回答3:

Maybe I am misunderstanding the question but isn't this just as simple as returning a list of variables, and the caller simply assigns each to a variable. That is

> function test () {return @('a','c'),'b'}
> $a,$b = test

$a will be an array, and $b the letter 'b'

> $a 
a
c
> $b
b