loops - 修改未枚举的对象时出错

Question

我有以下脚本:

$serverList = @{ 
    "Server1Name" = @{ "WindowsService1" = "Status"; "WindowsService2" = "Status" };
    "Server2Name" = @{ "WindowsService1" = "Status"; "WindowsService2" = "Status" };
    "Server3Name" = @{ "WindowsService1" = "Status" };
    "Server4Name" = @{ "WindowsService1" = "Status" };
    "Server5Name" = @{ "WindowsService1" = "Status" };
    "Server6Name" = @{ "WindowsService1" = "Status" }
}

$copy = $serverList.Clone()

foreach ($server in $copy.Keys) {
    foreach ($service in $copy[$server].Keys) {
        $serviceInfo = Get-Service -ComputerName $server -Name $service
        $serverList[$server][$service] = $serviceInfo.Status
    }
}

我确保没有修改正在枚举的哈希表，但在运行脚本时仍然收到此错误:

Collection was modified; enumeration operation may not execute.At line:14 char:14
+     foreach ($service in $copy[$server].Keys) {
+              ~~~~~~~~
    + CategoryInfo          : OperationStopped: (:) [], InvalidOperationException
    + FullyQualifiedErrorId : System.InvalidOperationException

我在这里读到了这一点:http://blog.matticus.net/2013/11/powershell-clearing-values-within.html 。如果我将代码表单复制到那里，它执行时不会出现错误。

我的问题可能与嵌套的 foreach 循环有关吗？我的代码有错误吗？有人能解释一下吗？

Answer 1

Powershell 不喜欢您修改正在迭代的集合。

一开始，您创建了一个名为 $copy 的克隆来避免此问题。 clone() 是“浅拷贝”，因此每个键引用的对象在副本中是相同的。

在这一行:

$serverList[$server][$service] = $serviceInfo.Status

您修改内部集合 - 您当前正在迭代该集合。

事实上，外部集合从未被修改，仅被引用，因此外部clone()调用是不必要的。相反，您应该克隆内部集合。 像这样的东西(未经测试):

$serverList = @{ 
    "Server1Name" = @{ "WindowsService1" = "Status"; "WindowsService2" = "Status" };
    "Server2Name" = @{ "WindowsService1" = "Status"; "WindowsService2" = "Status" };
    "Server3Name" = @{ "WindowsService1" = "Status" };
    "Server4Name" = @{ "WindowsService1" = "Status" };
    "Server5Name" = @{ "WindowsService1" = "Status" };
    "Server6Name" = @{ "WindowsService1" = "Status" }
}



foreach ($server in $serverList.Keys) {
   $copy = $serverList[$server].clone();
    foreach ($service in $copy.Keys) {
        $serviceInfo = Get-Service -ComputerName $server -Name $service
        $serverList[$server][$service] = $serviceInfo.Status
    }
}