How to define a function which requires one of two parameters? - powershell

Question

For the following function, it must have a parameter of Group of type int or a parameter of Items of type int array. How to define the function? It must have one of these parameters but cannot have both.
Start-Execute -Group 1
Start-Execute -Items 100,200,300

Answer 1

You want to use Parameter Sets, which are a feature of Advanced Functions.
function Start-Execute {
[CmdletBinding()]
param(
[Parameter(
ParameterSetName='ByGroup',
Mandatory=$true
)]
[int]
$Group ,
[Parameter(
ParameterSetName='ByItems',
Mandatory=$true
)]
[int[]]
$Items
)
# function code
}
Inside the function, you can determine which parameter set was specified by testing the value of $PSCmdlet.ParameterSetName to see which parameter set it matches.
To see that your parameter sets were created correctly, run the following after the function definition has been executed:
Get-Help Start-Execute
That will show you separate invocations for each parameter set.
That being said, we can't tell what your function does. If $Items is just meant to be an array of multiple $Groups (that is, a single item is the same as a group), then your function should accept a single int array [int[]] and then just always process it with foreach, because that will work correctly even with a single value supplied.
Adding a parameter to multiple parameter sets.
You asked about adding a parameter called -Debug. I just want to point out that -Debug is a Common Parameter, so you probably shouldn't use that name. I'll show an example using a parameter named -Test:
function Start-Execute {
[CmdletBinding()]
param(
[Parameter(
ParameterSetName='ByGroup',
Mandatory=$true
)]
[int]
$Group ,
[Parameter(
ParameterSetName='ByItems',
Mandatory=$true
)]
[int[]]
$Items ,
[Switch]
$Test
)
)
# function code
}
This is one way to do it: don't provide any parameter set names. It will be available in all sets.
Another way is to provide a separate [Parameter()] attribute for each parameter set:
[Parameter(
ParameterSetName='ByItems',
Mandatory=$true
)]
[Parameter(
ParameterSetName='ByGroup',
Mandatory=$false
)]
[Switch]
$Test
This is useful when you want to use different settings for different sets, such as to make this parameter mandatory in one parameter set but optional in another, or to make the parameter available to multiple but not all sets.