15-Advanced-Functions-in-Powershell.md

15. Advanced Functions in Powershell

Advanced Functions

• param statement

• Parameter attributes

  • Mandatory
  • ParameterSetName - closest to function overloading
  • Position
  • ValueFromPipeline

• Parameter Validation

  • AllowEmptyString
  • AllowNull
  • AllowEmptyCollection
  • ValidateLength
  • ValidatePattern
  • ValidateSet

• paramatrributes.ps1

function advancedfunction
{
    param (
    [Parameter (Mandatory = $True, Position = 0, ValueFromPipeline = $True, ParameterSetName="ParamSet1")]
    [ValidateSet(1,2,3)]
#   [AllowNull()]
    $a,

    [Parameter (Position = 1)]
    $b
    )

    Write-Output "a is $a"
    Write-Output "b is $b"
}

PS C:\Users\Administrator\Desktop\15> ls


    Directory: C:\Users\Administrator\Desktop\15


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
-a---         7/10/2017   6:25 PM        306 paramatrributes.ps1


PS C:\Users\Administrator\Desktop\15>

• Dot Sourcing

PS C:\Users\Administrator\Desktop\15> . .\paramatrributes.ps1

PS C:\Users\Administrator\Desktop\15> paramattributes 1 2
a is 1
b is 2
PS C:\Users\Administrator\Desktop\15>

PS C:\Users\Administrator\Desktop\15> paramattributes -a 2 -b 6
a is 2
b is 6
PS C:\Users\Administrator\Desktop\15>

PS C:\Users\Administrator\Desktop\15> paramattributes

cmdlet paramattributes at command pipeline position 1
Supply values for the following parameters:
a: 3
b: 4
a is 3
b is 4
PS C:\Users\Administrator\Desktop\15>

PS C:\Users\Administrator\Desktop\15> 1 | paramattributes -b 7
a is 1
b is 7
PS C:\Users\Administrator\Desktop\15>

PS C:\Users\Administrator\Desktop\15> paramattributes -a $null -b 6