Pass an unspecified set of parameters into a function and thru to a cmdlet - powershell

Question

Let's say I want to write a helper function that wraps Read-Host. This function will enhance Read-Host by changing the prompt color, calling Read-Host, then changing the color back (simple example for illustrative purposes - not actually trying to solve for this).
Since this is a wrapper around Read-Host, I don't want to repeat the all of the parameters of Read-Host (i.e. Prompt and AsSecureString) in the function header. Is there a way for a function to take an unspecified set of parameters and then pass those parameters directly into a cmdlet call within the function? I'm not sure if Powershell has such a facility.
for example...
function MyFunc( [string] $MyFuncParam1, [int] $MyFuncParam2 , Some Thing Here For Cmdlet Params that I want to pass to Cmdlet )
{
# ...Do some work...
Read-Host Passthru Parameters Here
# ...Do some work...
}

Answer 1

It sounds like you're interested in the 'ValueFromRemainingArguments' parameter attribute. To use it, you'll need to create an advanced function. See the about_Functions_Advanced and about_Functions_Advanced_Parameters help topics for more info.
When you use that attribute, any extra unbound parameters will be assigned to that parameter. I don't think they're usable as-is, though, so I made a little function that will parse them (see below). After parsing them, two variables are returned: one for any unnamed, positional parameters, and one for named parameters. Those two variables can then be splatted to the command you want to run. Here's the helper function that can parse the parameters:
function ParseExtraParameters {
[CmdletBinding()]
param(
[Parameter(ValueFromRemainingArguments=$true)]
$ExtraParameters
)
$ParamHashTable = #{}
$UnnamedParams = #()
$CurrentParamName = $null
$ExtraParameters | ForEach-Object -Process {
if ($_ -match "^-") {
# Parameter names start with '-'
if ($CurrentParamName) {
# Have a param name w/o a value; assume it's a switch
# If a value had been found, $CurrentParamName would have
# been nulled out again
$ParamHashTable.$CurrentParamName = $true
}
$CurrentParamName = $_ -replace "^-|:$"
}
else {
# Parameter value
if ($CurrentParamName) {
$ParamHashTable.$CurrentParamName += $_
$CurrentParamName = $null
}
else {
$UnnamedParams += $_
}
}
} -End {
if ($CurrentParamName) {
$ParamHashTable.$CurrentParamName = $true
}
}
,$UnnamedParams
$ParamHashTable
}
You could use it like this:
PS C:\> ParseExtraParameters -NamedParam1 1,2,3 -switchparam -switchparam2:$false UnnamedParam1
UnnamedParam1
Name Value
---- -----
switchparam True
switchparam2 False
NamedParam1 {1, 2, 3}
Here are two functions that can use the helper function (one is your example):
function MyFunc {
[CmdletBinding()]
param(
[string] $MyFuncParam1,
[int] $MyFuncParam2,
[Parameter(Position=0, ValueFromRemainingArguments=$true)]
$ExtraParameters
)
# ...Do some work...
$UnnamedParams, $NamedParams = ParseExtraParameters #ExtraParameters
Read-Host #UnnamedParams #NamedParams
# ...Do some work...
}
function Invoke-Something {
[CmdletBinding()]
param(
[Parameter(Mandatory=$true, Position=0)]
[string] $CommandName,
[Parameter(ValueFromRemainingArguments=$true)]
$ExtraParameters
)
$UnnamedParameters, $NamedParameters = ParseExtraParameters #ExtraParameters
&$CommandName #UnnamedParameters #NamedParameters
}
After importing all three functions, try these commands:
MyFunc -MyFuncParam1 Param1Here "PromptText" -assecure
Invoke-Something -CommandName Write-Host -Fore Green "Some text" -Back Red

Answer 2

One word: splatting.
Few more words: you can use combination of $PSBoundParameters and splatting to pass parameters from external command, to internal command (assuming names match). You would need to remove any parameter that you don't want to use though from $PSBoundParameters first:
$PSBoundParameters.Remove('MyFuncParam1')
$PSBoundParameters.Remove('MyFuncParam2')
Read-Host #PSBoundParameters
EDIT
Sample function body:
function Read-Data {
param (
[string]$First,
[string]$Second,
[string]$Prompt,
[switch]$AsSecureString
)
$PSBoundParameters.Remove('First') | Out-Null
$PSBoundParameters.Remove('Second') | Out-Null
$Result = Read-Host #PSBoundParameters
"First: $First Second: $Second Result: $Result"
}
Read-Data -First Test -Prompt This-is-my-prompt-for-read-host