Suppose I have this function;
Function SomeCommand{
param(
[string]$Var1,
[string]$Var2
)
# Do Something
}
I could set it up like this;
Function SomeCommand{
param(
[string]$Var1,
[string]$Var2
)
if ($Var2){
Do-SomeOtherCommand -SomeParam1 $Var1 -SomeParam2 $Var2
} else {
Do-SomeOtherCommand -SomeParam1 $Var1
}
This works fine if I only have one optional parameter, but if I have two it gets harry. I would like to do something like this;
Function SomeCommand{
param(
[string]$Var1,
[string]$Var2,
[string]$Var3
)
Do-SomeOtherCommand -SomeParam1 $Var1 (if($Var2){-SomeParam2 $Var2}) (if($Var3){-SomeParam3 $Var3})
}
Is there a way to accomplish this?
You are probably looking for splatting. You can build up a hashtable with the parameters you wish to pass (and their values), then specify the whole thing in one shot:
function FuncB($param1, $param2)
{
"FuncB -- param1:[$param1] param2:[$param2]"
}
function FuncA($paramA, $paramB)
{
$args = #{}
if ($paramA){ $args['param1'] = $paramA }
if ($paramB){ $args['param2'] = $paramB }
FuncB #args
}
Test
FuncA 'first' 'second'
FuncA 'OnlyFirst'
FuncA -paramB 'OnlySecond'
# results
# FuncB -- param1:[first] param2:[second]
# FuncB -- param1:[OnlyFirst] param2:[]
# FuncB -- param1:[] param2:[OnlySecond]
Semicolons. PowerShell allows you to use semicolons as line terminators.
Write-Output 1;Write-Output 2;Write-Output 3;
Personally, I think it should be mandatory.
Also note that you can build up an arbitrary expression as a simple string, then use Invoke-Expression (alias iex) to invoke it inline.
function FuncB($param1, $param2)
{
"FuncB -- param1:[$param1] param2:[$param2]"
}
function FuncA($paramA, $paramB)
{
$funcBCall = "FuncB $(if($paramA){ "-param1 '$paramA'" }) $(if($paramB){ "-param2 '$paramB'" })"
iex $funcBCall
}
This approach is very hacky and brittle, though, so I wouldn't recommend it.
Related
I want to wrap a function, that is to create a new function such that it would automatically pass some arguments to the old function, like python's partial functions. The arguments passed are the ones defined in the callee and not the caller. The important thing is that I don't want to refer to each of them explicitly (define them twice).
That is really done to save typing-in the same flags to complicated functions while allowing customization.
For example, in python, I would do:
call_with_x=partial(call,x=1)
or maybe use **kw and pass it to the callee in some cases .
This is my best try (based on Wrapper function in PowerShell: Pass remaining parameters) :
function Let
{
[CmdletBinding()]
Param([parameter(mandatory=$true, position=0)][string]$Option,
[parameter(mandatory=$false, position=1, ValueFromRemainingArguments=$true)]$Remaining)
Get #Remaining
}
function Get
{
[CmdletBinding()]
Param([parameter(mandatory=$false, position=0)][string]$OptionA,
[parameter(mandatory=$true, position=1)][string]$OptionB)
Write-Host $OptionA, $OptionB
}
But Let -Option c -OptionA 1
Prints -OptionA 1
which is obviously not what I intended.
If you don't require "advanced" function features from CmdletBinding(), then you can get away with using $args for this:
# simple function parameters are positional and named, but not mandatory
function let {
Param($OptionA,$OptionB)
write-host "OptionA=$OptionA"
write-host "OptionB=$OptionB"
get #args
}
function get {
Param($OptionC,$OptionD)
write-host "OptionC=$OptionC"
write-host "OptionD=$OptionD"
}
# not necessary to name or include parameters
let -OptionA A B -OptionC C D
OptionA=A
OptionB=B
OptionC=C
OptionD=D
# named parameters get assigned first, so the order is not too big a deal either
# these produce the same results as above:
let B -OptionA A D -OptionC C
let -OptionD D -OptionC C A B
Any named parameters will not get positionally assigned to let
Any additional parameters, named or otherwise, will be forwarded to get
That was hard!
For this you would need to add a bit of code in DynmaicParams and begin section of the function.
It might be possible to do it in an Attribute
function x{
[WrapperFor(y)]
Might do it Later.
function Get
{
[CmdLetBinding()]
Param([parameter(mandatory=$false, position=0)][string]$OptionA,
[parameter(mandatory=$false, position=1)][string]$OptionB)
Write-Host "opta",$OptionA
Write-Host "optb",$OptionB
}
function Let
{
[CmdletBinding()]
Param([parameter(mandatory=$true, position=0)][string]$Option,[parameter(mandatory=$false, position=0)][string]$OptionB)
DynamicParam {
AddWrapper -For "Get" -To "Let"
}
Begin {
$params = GetRestOfParams "Get" $PSBoundParameters
}
Process {
Get #params
}
}
Needed code:
using namespace System.Management.Automation
function Empt
{
[CmdletBinding()]
Param([parameter(mandatory=$true, position=0)][string]$aaaa)
1
}
function AddWrapper([parameter(mandatory=$true, position=0)][string]$For,[parameter(mandatory=$true, position=1)][string]$To)
{
$paramDictionary = [RuntimeDefinedParameterDictionary]::new()
$paramset= $(Get-Command $For).Parameters.Values | %{[System.Management.Automation.RuntimeDefinedParameter]::new($_.Name,$_.ParameterType,$_.Attributes)}
$paramsetlet= $(Get-Command empt).Parameters.Keys
$paramsetlet+= $(Get-Command $To).ScriptBlock.Ast.Body.ParamBlock.Parameters.Name | %{ $_.VariablePath.UserPath }
$paramset | %{ if ( -not ($paramsetlet -contains $_.Name) ) {$paramDictionary.Add($_.Name,$_)}}
return $paramDictionary
}
function GetRestOfParams($dst,$params)
{
$dstorgparams=$(Get-Command $dst).Parameters.Keys
$z= $params
$z.Keys | %{ if ( -not ($dstorgparams -contains $_) ) {$z.Remove($_)} } | Out-Null
return $z
}
I am writing a PowerShell module, the functions inside this module have some parameters which will be re-used across all functions. Rather than copy-pasting the function definition each time I add a new function, I would like to define them at the top like a script variable and then insert them into each function, giving me a single place to update if they need to be changed.
Looking at how dynamic parameters are defined it seems like I should be able to define an object of that type and then reference it in the function definitions, but I can't find anything online giving me the correct syntax to do this.
Using PowerShell version 7.2
$Script:ReUsedParameters = param(
[Parameter()]
[String]$Name,
[Parameter()]
[Int]$Id
)
Function New-Command {
Param ($ReUsedParameters)
Write-Output "Name: $Name, ID: $ID"
}
For the sake of answering, you can store the runtime parameters definitions in a script block and then call it & inside the function's dynamicparam block.
I do not think this is a good idea nor I recommend using this. All functions should have their own repeated param blocks if needed.
$reusedParameters = {
$paramDictionary = [System.Management.Automation.RuntimeDefinedParameterDictionary]::new()
# Since both parameters don't have any arguments (Mandatory, Position, ValueFromPipeline, etc..)
# you can use this one for both, otherwise, each dynamic parameter should have their own
# Parameter Declaration
[Parameter[]] $paramAttribute = [Parameter]::new()
$paramDictionary['Name'] = [System.Management.Automation.RuntimeDefinedParameter]::new('Name', [string], $paramAttribute)
$paramDictionary['Id'] = [System.Management.Automation.RuntimeDefinedParameter]::new('Id', [int], $paramAttribute)
return $paramDictionary
}
Function New-Command {
[CmdletBinding()] # `CmdletBinding` is Mandataroy here
param() # if the `param` block is empty
dynamicparam {
& $reusedParameters
}
end {
# Caveat: you can reference these parameters via $PSBoundParameters
# $Name and $Id are not part of the `param` block
# hence that wouldn't work here
"Name: {0}, ID: {1}" -f $PSBoundParameters['Name'], $PSBoundParameters['ID']
}
}
New-Command -Name asd -Id 123
As a declarative approach, you may turn the common parameters into class properties and have a single function parameter of the class type.
class MyReUsedParameters {
[String] $Name
[Int] $Id = 23
}
Function New-Command {
Param (
[MyReUsedParameters] $ReUsedParameters,
$AnotherParam
)
Write-Output "Name: $($ReUsedParameters.Name), ID: $($ReUsedParameters.ID)"
}
# Pass the common parameters as a hashtable which gets converted to
# MyReUsedParameters automatically.
New-Command -ReUsedParameters #{ Name = 'foo'; Id = 42 } -AnotherParam bar
# Alternatively pass the common parameters as a (typed) variable.
# PowerShell is able to deduce the argument name from the type.
$commonArgs = [MyReUsedParameters] #{ Name = 'Foo'; Id = 42 }
New-Command $commonArgs -AnotherParam bar
When passing a hashtable or PSCustomObject that has matching properties, it will automatically be converted to the class type.
You may even validate class properties similar to regular parameters. Most parameter validation attributes can be specified for class properties as well.
class MyReUsedParameters {
[ValidateNotNullOrEmpty()] [String] $Name
[Int] $Id = 23
# Constructor - required to apply validation
MyReUsedParameters( [Hashtable] $ht ) {
$this.Name = $ht.Name
$this.Id = $ht.Id
}
}
Function New-Command {
Param (
[Parameter(Mandatory)]
[MyReUsedParameters] $ReUsedParameters
)
Write-Output "Name: $($ReUsedParameters.Name), ID: $($ReUsedParameters.ID)"
}
# Causes an error (as expected), because Name property is missing
New-Command -ReUsedParameters #{ Id = 42 }
Consider two powershell functions:
function A {
params(
[Parameter()]$x,
[Parameter()]$y
)
Write-Host $x $y
}
function B {
params(
[Parameter()]$x,
[Parameter()]$z
)
Write-Host $x $z
}
I'd like to define a single parameter $x once (which could have fairly complex attributes that must be kept identical for both functions) and re-use it in both functions, so something like:
$x = {[Parameter()]$x}
function A {
params(
$x,
[Parameter()]$y
)
Write-Host $x $y
}
function B {
params(
$x,
[Parameter()]$z
)
Write-Host $x $z
}
(How) is this possible?
To reuse parameter declarations across functions - as requested in your question - see the following section.
To reuse parameter values (arguments) across functions, by way of presets (default value), see the bottom section.
In order to reuse parameter declarations - short of using design-time templating to generate source code - you need to to define a script block that creates a dynamic parameter that can be passed to the dynamicparam block of multiple advanced functions:
using namespace System.Management.Automation
# The script block that declares the dynamic parameter to be shared
# across functions.
$sharedDynParam = {
# Define the -x parameter dynamically.
$paramName = 'x'
$dict = [RuntimeDefinedParameterDictionary]::new()
$dict.Add(
$paramName,
[RuntimeDefinedParameter]::new(
$paramName,
[datetime], # Type the parameter [datetime]. for instance.
[ParameterAttribute] #{
Mandatory = $true # Make the parameter mandatory, for instance.
# ParameterSetName = 'default' # Assign it to a parameter set, if neeeded.
}
)
)
# Return the dictionary
return $dict
}
function A {
[CmdletBinding()]
param(
$y
)
# Assign the shared dynamic parameter.
dynamicparam { & $sharedDynParam }
# The use of `dynamicparam { ... }` requires use of an explicit
# `process { ... }` block (and optionally `begin { ... }` and
# `end { ... }`, as needed).
process {
# Note: A dynamic -x parameter cannot be accessed as $x
# Instead, it must be accessed via the $PSBoundParameters dictionary.
"[$($PSBoundParameters['x'])] - [$y]"
}
}
function B {
[CmdletBinding()]
param(
$z
)
# Assign the shared dynamic parameter.
dynamicparam { & $sharedDynParam }
process {
"[$($PSBoundParameters['x'])] - [$z]"
}
}
# Sample calls,
A -x '1970-01-01' -y yval
B -x '1970-01-02' -z zval
Output:
[01/01/1970 00:00:00] - [yval]
[01/02/1970 00:00:00] - [zval]
To preset the value of a parameter by a given name across commands, use the $PSDefaultParameterValues preference variable:
# Preset a parameter value for all commands ('*') that have
# an -x ('x') parameter.
$PSDefaultParameterValues = #{ '*:x' = [pscustomobject] #{ foo = 1; bar = 2 } }
function A {
[CmdletBinding()] # This makes the function an *advanced* one, which respects
# $PSDefaultParameterValues; similarly, at least one
# parameter-individual [Parameter()] attribute does the same.
param(
$x,
$y
)
"[$x] - [$y]"
}
function B {
[CmdletBinding()]
param(
$x,
$z
)
"[$x] - [$z]"
}
# Sample calls, without an -x argument, relying on
# $PSDefaultParameterValues to provide it automatically.
A -y yval
B -z zval
Output, showing that parameter -x was automatically bound via $PSDefaultParameterValues:
[#{foo=1; bar=2}] - [yval]
[#{foo=1; bar=2}] - [zval]
I am trying to write a simple wrapper that accept one parameter for the output.
This is how it looks now
function Get-data{
param (
[switch]$network,
[switch]$profile,
[switch]$server,
[switch]$devicebay
)
if ($network.IsPresent) { $item = "network"}
elseif ($profile.IsPresent) {$item = "profile"}
elseif ($server.IsPresent) {$item = "server"}
elseif ($devicebay.IsPresent){$item = "devicebay"}
$command = "show $item -output=script2"
}
Clearly this could be optimize but I am struggling to wrap my head around on how I can achieve it .Is there some easy way to ensure only single parameter is accepted and used without resorting to multiple elseif statements?
Also I would like to provide array of paramters instead doing it the way it is done at the moment.
Another thing you could do instead of all those switch parameters is to use a [ValidateSet]
function Get-Data{
[cmdletbinding()]
param(
[Parameter(Mandatory=$true)]
[ValidateSet('Network','Profile','Server','DeviceBay')]
[string]$Item
)
Switch ($Item){
'network' {'Do network stuff'}
'profile' {'Do profile stuff'}
'server' {'Do server stuff'}
'devicebay' {'Do devicebay stuff'}
}
}
Probably not the most elegant solution, but using parametersets makes powershell do some of the work for you:
#requires -version 2.0
function Get-data {
[cmdletbinding()]
param(
[parameter(parametersetname="network")]
[switch]$network,
[parameter(parametersetname="profile")]
[switch]$profile,
[parameter(parametersetname="server")]
[switch]$server,
[parameter(parametersetname="devicebay")]
[switch]$devicebay
)
$item = $PsCmdlet.ParameterSetName
$command = "show $item -output=script2"
}
This example will error out if you don't provide one of the switches, but you could probably provide an extra switch that does nothing or errors more gracefully if you want to account for that case...
You can add the [cmdletbinding()] keyword so you get $PSBoundParameters, and use that for a switch pipeline:
function Get-data{
[cmdletbinding()]
param (
[switch]$network,
[switch]$profile,
[switch]$server,
[switch]$devicebay
)
Switch ($PSBoundParameters.GetEnumerator().
Where({$_.Value -eq $true}).Key)
{
'network' { 'Do network stuff' }
'profile' { 'Do profile stuff' }
'server' { 'Do server stuff' }
'devicebay' { 'Do devicebay stuff' }
}
}
Since you want only one switch to be enabled, an enum might help you.
This way, you're not using a switch but a standard parameter - still, the user of the cmdlet can use TAB to autocomplete the values that may be entered.
Just set the type of the parameter to your enum.
I'm trying to make use of the $args array with a pipeline parameter.
The function expects an arbitrary number of parameters (e.g. param0) following the first, pipelined parameter:
function rpt-params {
param (
[Parameter(ValueFromPipeline=$true,Position=0,Mandatory=$true)][CrystalDecisions.CrystalReports.Engine.ReportDocument]$reportDocument
)
try {
write-host "count: " $args.count
#TODO process args
}
catch [Exception] {
write-host $_.Exception
}
finally {
return $reportDocument
}
}
Attempts to call the function produce an error that reads "rpt-params : A parameter cannot be found that matches parameter name 'param0'.":
...
# syntax 0
rpt-params $rpt -param0 "mb-1" -param1 "me-1"
...
...
# syntax 1; explicitly naming the first parameter
rpt-params -reportDocument $rpt -param0 "mb-1" -param1 "me-1"
...
Is my syntax the issue or is it related to using a pipelined parameter?
Create another parameter, called it something like $rest and decorate it with [Parameter(ValueFromRemainingArguments = $true)].
When you use "[cmdletbinding()]" or "[Parameter()]", which is the case here, your Function turns into an Advanced Function. An Advanced Function can only take the Arguments that are specified under "Param" and no more. To make your Function act like before, like Keith recommends, you'll need to add [Parameter(ValueFromRemainingArguments = $true)]
For Example:
function rpt-params {
param (
[Parameter(ValueFromPipeline=$true,Position=0,Mandatory=$true)]
[CrystalDecisions.CrystalReports.Engine.ReportDocument]$reportDocument,
[Parameter(ValueFromRemainingArguments=$true)]$args
)
try {
write-host "count: " $args.count
#TODO Now args can have all remaining values
}
catch [Exception] {
write-host $_.Exception
}
finally {
return $reportDocument
}
}