Question

对于我正在进行的项目，我需要检查并查看文件中的一行中是否存在一对字符串。

我试过使用这样的哈希表：

$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza'

$table = @{}

for ($i = 0; $i -lt $makes.Length; $i++)
{
    $table.Add($makes[$i], $models[$i])
}

这很有效，直到我尝试插入重复的make。我很快发现散列表不接受重复。

那么有没有办法在PowerShell中创建双重字符串列表？在C＃中很容易做到，但我发现无法在PowerShell中实现它。

Answer 1

对代码和逻辑进行最小的更改：

$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza'

for ($i = 0; $i -lt $makes.Length; $i++){
    [array]$cars += New-Object psobject -Property @{
        make  = $makes[$i]
        model = $models[$i]

    }
}

这会使用自定义psobject投射到数组，以便允许+=。

Answer 2

这是一种避免数组连接的方法（类似于Python“list comprehension”语法）：

$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza'

$cars = 0..$makes.Length | ForEach-Object {
  [PSCustomObject] @{
    Make  = $makes[$_]
    Model = $models[$_]
  }
}

Answer 3

您可以使用PSCustomObject并直接填充列表：

$cars = @(
    [pscustomobject]@{make = "Ferrari"; model="Enzo"}
    [pscustomobject]@{make = "Ford"; model="Focus"}
    [pscustomobject]@{make = "Peugeot"; model="206"}
    [pscustomobject]@{make = "Subaru"; model="Imprezza"}
)

Answer 4

如果将与给定品牌相关联的所有型号存储为数组，您仍然可以使用哈希表 - 使用方便的基于密钥的查找每个制作 - 根据定义一个也是唯一的 - 条目：

# Note the duplicate 'VW' entry at the end.
$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru', 'VW'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza', 'Polo'

$table = [ordered] @{}; $i=0  # [ordered] (PSv3+) preserves the order of the keys
foreach($make in $makes) {
  # Add the model at hand to the make's array.
  # The entry is created on demand as an array, due to [object[]]
  # ([array] works too, but it is [object[]] that is actually created),
  # and for additional models the array is appended to.
  # You could also use [string[]], specifically.
  [object[]] $table[$make] += $models[$i++]
}

# Output the resulting hashtable
$table

这会产生：

Name                           Value                                                                                                                                               
----                           -----                                                                                                                                               
Ferrari                        {Enzo}                                                                                                                                              
Ford                           {Focus}                                                                                                                                             
VW                             {Golf, Polo}                                                                                                                                        
Peugeot                        {206}                                                                                                                                               
Subaru                         {Impreza}

请注意VW的值 2 条目（{...}表示某个值是数组）。

要稍后获得给定品牌的型号，只需使用：

$vwModels = $table['VW']

检查表中是否已包含给定的品牌/型号对：

$table[$make] -contains $model

请注意，使用+=扩展数组很方便，但很慢，因为实际上每次都必须创建 new 数组。

如果效果重要，请改为使用[System.Collections.ArrayList]或通用[System.Collections.Generic.List[<type>]]实例：

# Note the duplicate 'VW' entry at the end.
$makes = 'Ferrari', 'Ford', 'VW', 'Peugeot', 'Subaru', 'VW'
$models = 'Enzo', 'Focus', 'Golf', '206', 'Impreza', 'Polo'

$table = [ordered] @{}; $i=0  # [ordered] (PSv3+) preserves the order of the keys
foreach($make in $makes) {
  # Add the model at hand to the make's array list.
  # Note the need to assign an *array* (when the entry is created),
  # using the prepended array-construction operator, ",", which is preferable
  # to @(...) for performance reasons.
  # [Collections.Generic.List[string]] would work too.
  [Collections.ArrayList] $table[$make] += , $models[$i++]
}

# Output the resulting hashtable
$table

请注意，PowerShell如何仅允许您使用[Collections.ArrayList]而不是完整类型名称[System.Collections.ArrayList]，因为隐含了第一个组件System。

在PowerShell中创建配对字符串值的列表

4 个答案: