Powershell 5類和單身人士

Question

是否有正確/最好/任何方式使用PowerShell 5.0中的類結構來構建單例類？我已經試過這樣的事情：

class ScannerGeometry 
{ 
    [int] $EEprom;    # read eeprom 
    # .... 

    ScannerGeometry() 
    { 
     # ... fetch calibration from instrument 
    } 

    [ScannerGeometry] Instance() { 
     if ($this -eq $null) 
     { 
      $this = [ScannerGeometry]::new() 
     } 
     return $this 
    } 
} 

並賦予它的東西，如：

$scanner = [ScannerGeometry]::Instance() 

唉，我收到的Method invocation failed because [ScannerGeometry] does not contain a method named 'Instance'.

而且運行時錯誤，可能使一個構造函數（或任何其他方法）私人在PS5類？

Answer 1

你的方法是這樣的可見的，因爲它不是一成不變的：

[ScannerGeometry]::new() | set x 
PS C:\Work> $x | gm 


    TypeName: ScannerGeometry 

Name  MemberType Definition 
----  ---------- ---------- 
Equals  Method  bool Equals(System.Object obj) 
GetHashCode Method  int GetHashCode() 
GetType  Method  type GetType() 
Instance Method  ScannerGeometry Instance() 
ToString Method  string ToString() 
EEprom  Property int EEprom {get;set;} 

您需要使用關鍵字static。在這種情況下，$this是無效的，所以你必須稍微改變一下代碼。下面是代碼：

class ScannerGeometry 
{ 
    [int] $EEprom;    # read eeprom 


    static [ScannerGeometry] Instance() { 
      return [ScannerGeometry]::new() 
    } 
} 

---

編輯

好，這裏是工作代碼：

class ScannerGeometry 
{ 
    [int] $EEprom    # read eeprom 

    static [ScannerGeometry] $instance 


    static [ScannerGeometry] GetInstance() { 
      if ([ScannerGeometry]::instance -eq $null) { [ScannerGeometry]::instance = [ScannerGeometry]::new() } 
      return [ScannerGeometry]::instance 
    } 
} 

$s = [ScannerGeometry]::GetInstance() 

Answer 2

這個怎麼樣？

class ScannerGeometry 
{ 
    [int] $EEprom;    # read eeprom 
    # .... 

    ScannerGeometry() 
    { 
     # ... fetch calibration from instrument 
    } 

    [ScannerGeometry] Instance() { 
     if ($this -eq $null) 
     { 
      $this = [ScannerGeometry]::new() 
     } 
     return $this 
    } 
} 

$scangeo = [ScannerGeometry]::new().Instance() 

PS：代碼只給沒有錯誤，我完全無能的單身方面:(

Source : HSGB