如何设置 PowerShell 的默认输出 class

Question

我正在尝试创建一个从标准 [Data.DataTable] class 派生的 PowerShell [DataTable] class 以简化数据的创建 tables:
_{（另见：#11987 Accelerated [DataTable] with easy constructor and AddRow method）}

class DataTable : Data.DataTable {
    [ValidateNotNullOrEmpty()][Data.DataTable]$DataTable
    DataTable([Array]$ColumnNames) {
        $This.DataTable = New-Object Data.DataTable
        ForEach ($ColumnName in $ColumnNames) {
            If ($ColumnName -is [System.Collections.IDictionary]) {
                ForEach($Key in $ColumnName.Get_keys()) { $This.AddColumn($Key, $ColumnName[$Key]) }
            } Else { $This.AddColumn($ColumnName) }
        }
    }
    [Void]AddColumn([String]$ColumnName) {
        $DataColumn = New-Object Data.DataColumn($ColumnName)
        $This.DataTable.Columns.Add($DataColumn)
    }
    [Void]AddColumn([String]$ColumnName, [Type]$ColumnType = [String]) {
        $DataColumn = New-Object Data.DataColumn($ColumnName, $ColumnType)
        $This.DataTable.Columns.Add($DataColumn)
    }
    [Void]AddRow([Array]$Array) {
        $DataRow = $This.DataTable.NewRow()
        For ($i = 0; $i -lt $Array.Length; $i++) { $DataRow.Item($i) = $Array[$i] }
        $This.DataTable.Rows.Add($DataRow)
    }
    [Void]AddRow([System.Collections.IDictionary]$Dictionary) {
        $DataRow = $This.DataTable.NewRow()
        ForEach ($Name in $Dictionary.get_Keys()) { $DataRow.Item($Name) = $Dictionary[$Name] }
        $This.DataTable.Rows.Add($DataRow)
    }
}

它适用于创建新数据table:

$MyDataTable = [DataTable]('a', 'b', 'c')
$MyDataTable.AddRow(@(1,2,3))

但要获得 $DataTable 需要做的事情：

$MyDataTable.DataTable
a b c
- - -
1 2 3

我希望它默认输出数据 table $MyDataTable~~.DataTable~~ 并执行如下操作：

$MyDataTable | ForEach-Object { ...

如何让我的 class 默认为 return $This.DataTable？
（或者这对于 PowerShell class 根本不可能吗？）

更新
class 中有一些（与问题无关的）错误，我在下面连同 @Adam Luniewski.

的答案一起修复了这些错误

class DataTable : Data.DataTable {

    DataTable([Array]$ColumnNames) {
        ForEach ($ColumnName in $ColumnNames) { $This.AddColumn($ColumnName) }
    }
    DataTable([System.Collections.IDictionary]$ColumnNameTypes) {
        ForEach($Key in $ColumnNameTypes.Get_keys()) { $This.AddColumn($Key, $ColumnNameTypes[$Key]) }
    }
    [Void]AddColumn([String]$ColumnName) {
        $DataColumn = New-Object Data.DataColumn($ColumnName)
        $This.Columns.Add($DataColumn)
    }
    [Void]AddColumn([String]$ColumnName, [Type]$ColumnType = [String]) {
        $DataColumn = New-Object Data.DataColumn($ColumnName, $ColumnType)
        $This.Columns.Add($DataColumn)
    }
    [Void]AddRow([Array]$Array) {
        $DataRow = $This.NewRow()
        For ($i = 0; $i -lt $Array.Length; $i++) { $DataRow.Item($i) = $Array[$i] }
        $This.Rows.Add($DataRow)
    }
    [Void]AddRow([System.Collections.IDictionary]$Dictionary) {
        $DataRow = $This.NewRow()
        ForEach ($Name in $Dictionary.get_Keys()) { $DataRow.Item($Name) = $Dictionary[$Name] }
        $This.Rows.Add($DataRow)
    }
}

Answer 1

您的新 class 正在扩展 DataTable，因此它已经是 DataTable。您不需要内部 DataTable 并且可以对 $This 而不是 $This.DataTable 执行所有操作。我只将 class 的名称更改为 MyDataTable 并删除了内部数据表：

class MyDataTable : Data.DataTable {

  MyDataTable([Array]$ColumnNames) {
      ForEach ($ColumnName in $ColumnNames) {
          If ($ColumnName -is [System.Collections.IDictionary]) {
              ForEach($Key in $ColumnName.Get_keys()) { $This.AddColumn($Key, $ColumnName[$Key]) }
          } Else { $This.AddColumn($ColumnName) }
      }
  }
  [Void]AddColumn([String]$ColumnName) {
      $DataColumn = New-Object Data.DataColumn($ColumnName)
      $This.Columns.Add($DataColumn)
  }
  [Void]AddColumn([String]$ColumnName, [Type]$ColumnType = [String]) {
      $DataColumn = New-Object Data.DataColumn($ColumnName, $ColumnType)
      $This.Columns.Add($DataColumn)
  }
  [Void]AddRow([Array]$Array) {
      $DataRow = $This.NewRow()
      For ($i = 0; $i -lt $Array.Length; $i++) { $DataRow.Item($i) = $Array[$i] }
      $This.Rows.Add($DataRow)
  }
  [Void]AddRow([System.Collections.IDictionary]$Dictionary) {
      $DataRow = $This.NewRow()
      ForEach ($Name in $Dictionary.get_Keys()) { $DataRow.Item($Name) = $Dictionary[$Name] }
      $This.Rows.Add($DataRow)
  }
}

$MyDataTable = [MyDataTable]('a', 'b', 'c')
$MyDataTable.AddRow(@(1,2,3))

$MyDataTable #works now:


a b c
- - -
1 2 3

如何设置 PowerShell 的默认输出 class

How to set the default output of a PowerShell class

powershell

class

return-value