Return PowerShell 中具有单个元素的数组

Question

这应该非常简单 - 我需要 return 来自函数的哈希表数组。这在有多个散列表时有效，但当只有一个散列表时，结果不是数组。我宁愿不测试结果是否为数组。

function GetArrayWith1Hashtable()
{
    $array = @()

    $hashtable = @{}
    $hashtable["a"] = "a" 
    $hashtable["b"] = "b" 
    $hashtable["c"] = "c"
    $array += $hashtable 

    Write-Host "GetArrayWith1Hashtable array.Length =" $array.Length
    Write-Host "GetArrayWith1Hashtable array.Count" $array.Count
    Write-Host "GetArrayWith1Hashtable array[0].Keys" $array[0].Keys

    $array
}

function GetArrayWith2Hashtables()
{
    $array = @()

    $hashtable = @{}
    $hashtable["a"] = "a" 
    $hashtable["b"] = "b" 
    $hashtable["c"] = "c"
    $array += $hashtable 

    $hashtable2 = @{}
    $hashtable2["d"] = "d" 
    $hashtable2["e"] = "e"
    $hashtable2["f"] = "f"
    $array += $hashtable2 

    Write-Host "GetArrayWith2Hashtables array.Length = " $array.Length
    Write-Host "GetArrayWith2Hashtables array.Count = " $array.Count
    Write-Host "GetArrayWith2Hashtables array[0].Keys =" $array[0].Keys
    Write-Host "GetArrayWith2Hashtables array.Count = "$array[1].Keys

    $array
}

$result1 = GetArrayWith1Hashtable
# $result1.Length - not available
Write-Host "Result of GetArrayWith1Hashtable result1.Count = " $result1.Count                      # Count = 2 (would expect this to be 1)
# $result1[0] not available - not an array

$result2 = GetArrayWith2Hashtables
Write-Host "Result of GetArrayWith2Hashtables result2.Length = "    $result2.Length # Length = 2
Write-Host "Result of GetArrayWith2Hashtables result2.Count = "     $result2.Count # Count = 2
Write-Host "Result of GetArrayWith2Hashtables result2[0].Keys = "     $result2[0].Keys # Keys = c a b
Write-Host "Result of GetArrayWith2Hashtables result2[1].Keys = "     $result2[1].Keys # Keys = d e f

 <#
  FULL OUTPUT:

 GetArrayWith1Hashtable array.Length = 1
 GetArrayWith1Hashtable array.Count 1
 GetArrayWith1Hashtable array[0].Keys c a b

 Result of GetArrayWith1Hashtable result1.Count =  2

 GetArrayWith2Hashtables array.Length =  2
 GetArrayWith2Hashtables array.Count =  2
 GetArrayWith2Hashtables array[0].Keys = c a b
 GetArrayWith2Hashtables array.Count =  d e f

 Result of GetArrayWith2Hashtables result2.Length =  2
 Result of GetArrayWith2Hashtables result2.Count =  2
 Result of GetArrayWith2Hashtables result2[0].Keys =  c a b
 Result of GetArrayWith2Hashtables result2[1].Keys =  d e f

 #>

Answer 1

只需将 return 类型转换为数组：

$result1 = @(GetArrayWith1Hashtable)

Answer 2

实际上，您只需在 returned 项目前添加逗号即可。这告诉 PowerShell 按原样 return 它，而不是试图聪明地对待它。这也允许您在一个地方修复它，而不是在它被调用的所有地方。

function GetArrayWith1Hashtable()
{
    $array = @()

    $hashtable = @{}
    $hashtable["a"] = "a" 
    $hashtable["b"] = "b" 
    $hashtable["c"] = "c"
    $array += $hashtable 

    Write-Host "GetArrayWith1Hashtable array.Length =" $array.Length
    Write-Host "GetArrayWith1Hashtable array.Count" $array.Count
    Write-Host "GetArrayWith1Hashtable array[0].Keys" $array[0].Keys

    # The only edit was to add the comma below
    ,$array
}

更新： 虽然，我认为您不需要此功能，但我会提及它，以便其他人能够理解其中的区别并为他们的方法做出明智的选择。

为了使您的函数兼容以便在管道中更有效地使用，更好的方法是为每个项目调用 Write-Output。

function GetArrayWith1Hashtable()
{
    Write-Output "a" 
    Write-Output "b" 
    Write-Output "c"
}

通过使用 Write-Output，您允许 PowerShell 调用下一个命令的 Process block in the pipeline, individually for each object. Otherwise it would call the next command and pass a single array object to it. You can read more about piping objects here

Return PowerShell 中具有单个元素的数组

Return array with single element in PowerShell

arrays

powershell

hashtable

powershell-5.0