在 PowerShell 中调用动态变量 [英] Calling dynamic variable in PowerShell

问题描述

我正在尝试创建一个新变量，该变量将使用其他具有动态名称的变量作为其值.这是我想要做的:

I am trying to create a new variable that would use other variable with dynamic name as its value. Here's what I am trying to do:

我有一个带有两个值的 System.Array:

I have a System.Array with two values:

$Years = 2015, 2016

另一个变量 $Transactions 包含各种交易的列表.

Another variable $Transactions has a list of various transactions.

我试图通过以下方式使用每个 $Years 值:

I am trying to use each of those $Years values in the following way:

ForEach($Year in $Years){

New-Variable -Name "Transactions_$Year" -Value $Transactions | Where {$_.Date -like "*.$Year"

现在我想做的(在同一个 ForEach 循环中)是在创建另一个新变量时使用该 $Transactions_$Year 值，如下所示:

Now what I would like to do (within that same ForEach-loop) is to use that $Transactions_$Year value when I am creating a another new variable, like this:

New-Variable -Name "Income_$Year" -Value $Transactions_$Year |  Where {$_.Amount -NotLike "-*"} | Measure-Object Amount -Sum | Select -ExpandProperty Sum

}

这可能吗，或者您有什么其他方法可以实现这一目标?

Is this possible, or do you have any alternative ways how I could achieve this?

推荐答案

首先，您的 New-Variable 调用没有按照您的想法执行，因为您需要通过管道传输输出New-Variable 到 Where-Object 而不是使用 $Transactions | 的值其中 ... 作为变量的值.你需要括号才能工作:

First of all, your New-Variable invocation doesn't do what you think it does, as you'd pipe the output of New-Variable to Where-Object instead of using the value of $Transactions | Where ... as value for the variable. You need parentheses for that to work:

New-Variable -Name "Transactions_$Year" -Value ($Transactions | Where {$_.Date -like "*.$Year" })

如果你绝对必须使用这种方法，那么你可以通过Get-Variable再次获取变量:

If you absolutely have to use this approach, then you can get the variables again via Get-Variable:

Get-Variable Transactions_$Year | % Value

然而，具有魔法名称的多个变量是一种相当糟糕的解决方法.你可能更想要一张地图:

However, multiple variables with magic names is a rather poor way of solving this. You probably rather want a map:

$TransactionsPerYear = @{}
$Years | ForEach-Object {
  $TransactionsPerYear[$_] = $Transactions | Where Date -like "*.$_"
}

您可以使用 $TransactionsPerYear[2015] 获取 2015 年的所有交易.

And you can get all transactions for 2015 with $TransactionsPerYear[2015].

另一种方法是Group-Object，它甚至不需要可能的年份列表开始，而是根据某些属性或表达式结果对多个对象进行分组:

Another way is Group-Object which doesn't even require a list of possible years to begin with, but groups a number of objects by some property or expression result:

$TransactionsPerYear = $Transactions | Group-Object { [int]($_.Date -replace '.*.') }

(这是对它如何工作的猜测.似乎您的日期字符串最多包含一个句点，之后是年份而没有其他内容，所以可能类似于 dd.MM.yyyy 日期格式.

(This is a guess on how it could work. It seems like your date string contains something up to a period, after which there is the year and nothing else, so perhaps something like dd.MM.yyyy date format.

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