PowerShell - how to add private members?

问题:

In PowerShell (v2), how do you add private members to a PSObject?

That is, members that can only be accessed via $this from within a ScriptProperty or ScriptMethod.

回答1:

Prior to the introduction of classes in version 5.0, the PowerShell extended type system (ETS) doesn't have the same concept of access modifiers as the underlying type system (.NET/CTS) has.

One way of hinting at "don't use this directly" to users, would be to have a prefix for "internal" properties, like __ (double underscore):

$object = New-Object psobject -Property @{
    Public    = 4
    __private = 9
} |Add-Member -MemberType ScriptProperty -Name Private -Value {
    $this.__private 
  } -SecondValue { 
    param([int]$newValue) 

    if(($newValue % 3) -ne 0){
      Write-Warning "Only multiples of 3 allowed"
    } else {
      $this.__private = $newValue
    }
} -PassThru