I'm trying to pass a function to a method and then pass parameters to the method I passed when calling it, but if I pass more than one parameter then the method fails with an error:
function debugMeStuffs($someBlah, $somePoo) {
Write-Host $someBlah
Write-Host $somePoo
}
function invokeOnHosts ([scriptblock]$funcToCall, $param1, $param2, $startRange, $endRange) {
#Param($funcToCall)
$i = $startRange
for($i = [int]$startRange; $i -le $endRange; $i++) {
# HOW DO I MAKE THIS WORK WITH MULTIPLE PARAMETERS?!?!?!?
$funcToCall.Invoke('blah' 'poo')
}
}
invokeOnHosts $function:debugMeStuffs "param1" "param2" 4 7
Things I've tried:
$funcToCall("blah" "poo")
$funcToCall('blah' 'poo')
$funcToCall.Invoke("blah" "poo")
$funcToCall.Invoke('blah' 'poo')
$funcToCall 'blah' 'poo'
$funcToCall.Invoke 'blah' 'poo'
$funcToCall "blah" "poo"
$funcToCall.Invoke "blah" "poo"
None of the above seem to work. Is there something else I need to do to make this work?
.Invoke()
is a .NET method , so the usual method-call syntax applies : you need
(...)
- around the list of arguments ,
$funcToCall.Invoke('blah', 'poo')
This contrasts with PowerShell's own syntax for calling cmdlets and functions , which is shell-like [1] :
no (...)
around the argument list
arguments must be separated with spaces .
& $funcToCall blah poo # equivalent of the method call above.
A command such as the above is parsed in argument mode , which is why quoting the arguments in this simple case is optional .
Note the need for &
, PowerShell's call operator , which is needed to execute the script block stored in $funcToCall
; this is generally necessary for invoking a command stored in a variable , and also for command names / paths that are quoted .
Given that it's easy to get confused between PowerShell's command syntax and .NET's method syntax, it's best to stick with PowerShell-native features [2] , if possible.
That said, being able to call methods on .NET types directly is a wonderful extensibility option.
To help avoid accidental use of method syntax when calling PowerShell commands, you can use Set-StrictMode -Version 2
or higher, but note that that entails additional strictness checks.
[1] PowerShell is, after all, a shell - but it is also a full-featured scripting language that offers near-unlimited access to the .NET framework.
Reconciling these two personalities is a difficult balancing act, and the shell-like command-invocation syntax is a frequent problem for newcomers with a programming background, given that the rest of the language looks like a traditional programming language and that calling methods on .NET types does use the traditional syntax.
[2] This means preferring PowerShell's cmdlets, functions, and operators to use of the underlying .NET types' methods; doing so also usually provides rewards you with operating at a higher level of abstraction.
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