Reference Static member in Static Method In a Powershell Class

Question

Why does the direct access of a static fail, but the indirect works? Note that the file loaded is valid in both examples.

Failure Using Direct To Static

class OpPrj {

[string] $ProjectPath

static [string] $configFile = 'settings.json';

[OpPrj] static GetSettings(){
   return [OpPrj](Get-Content [OpPrj]::configFile | Out-String|ConvertFrom-Json);
}

Works By Assigning to Local

class OpPrj {

  [string] $ProjectPath

  static [string] $configFile = 'settings.json';

  [OpPrj] static GetSettings(){
      $file = [OpPrj]::configFile
      Write-Host $file  # outputs settings.json
      return [OpPrj](Get-Content $file | Out-String | ConvertFrom-Json);
  }

Because your syntax is wrong: (Get-Content ([OpPrj]::configFile) | ... This is the way you need to reference static properties for any type (or enum!) when dealing with parameter binding, that is, wrapped in parens. I don't understand why the parser works that way here, but it does. — Maximilian Burszley
– Maximilian Burszley, Commented Mar 13, 2019 at 14:32
Shouldn't you be using the $this automatic variable instead of [OpPrj]::configFile ? — Theo
– Theo, Commented Mar 13, 2019 at 14:33
@Theo $this doesn't exist for static members because they exist on the type not the object. — Maximilian Burszley
– Maximilian Burszley, Commented Mar 13, 2019 at 14:33
@TheIncorrigible1 Ah, I didn't know that. Thanks for the heads-up. — Theo
– Theo, Commented Mar 13, 2019 at 14:34
@TheIncorrigible1 Put it as an answer, and I will mark it as such. thx! — ΩmegaMan
– ΩmegaMan, Commented Mar 13, 2019 at 14:37

Maximilian Burszley · Accepted Answer · 2019-03-13 14:45:12Z

3

You have a syntax error in your call to Get-Content:

Get-Content [OpPrj]::configFile

The PowerShell parser is unable to determine where this ends (I am uncertain of the reason), so you need to explicitly wrap it in parentheses (I also recommend being explicit about the parameter you're passing, especially in scripts, for readability):

Get-Content -Path ([OpPrj]::configFile)

You will need to follow this syntax for enums and static class members.

In all (your call to Out-String is unnecessary):

class OpPrj
{
    [string] $ProjectPath

    static [string] $ConfigFile = 'settings.json'

    static [OpPrj] GetSettings()
    {
        return [OpPrj](Get-Content -Path ([OpPrj]::ConfigFile) -Raw | ConvertFrom-Json)
    }
}

edited Mar 13, 2019 at 14:45

answered Mar 13, 2019 at 14:39

Maximilian Burszley

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1 Comment

ΩmegaMan Over a year ago

Mr. Ohio...thank you for the info on Out-String too. :-)

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