当你调用某个函数时，PowerShell会增加一次嵌套层次。当一个函数调用了另一个函数，或着脚本，也会增加嵌套层次。今天分享一个函数，它能告诉你的脚本嵌套的层次：
function Test-NestLevel
{
$i = 1
$ok = $true
do
{
try
{
$test = Get-Variable -Name Host -Scope $i
}
catch
{
$ok = $false
}
$i++
} While ($ok)
$i
}
当你调用的函数具有递归调用时，上面的函数非常有用，来看一个调用的示例:
function Test-Diving
{
param($Depth)
if ($Depth -gt 10) { return }
"Diving deeper to $Depth meters..."
$currentDepth = Test-NestLevel
"calculated depth: $currentDepth"
Test-Diving -depth ($Depth+1)
}
Test-Diving -depth 1
当你运行Test-Diving时，函数会调用自己10次。函数使用一个参数来控制嵌套层次，而Test-NestLevel负责返回确切的深度数。
注意这里有个区别：Test-NestLevel返回绝对的嵌套层次，参数会纪录这个函数调用自己多少次。如果Test-Diving被嵌入到另外一个函数中，绝对深度和相对深度会不同。
PS C:\> Test-Diving -Depth 1
diving deeper to 1 meters...
calculated depth: 1
diving deeper to 2 meters...
calculated depth: 2
diving deeper to 3 meters...
calculated depth: 3
diving deeper to 4 meters...
calculated depth: 4
diving deeper to 5 meters...
calculated depth: 5
diving deeper to 6 meters...
calculated depth: 6
diving deeper to 7 meters...
calculated depth: 7
diving deeper to 8 meters...
calculated depth: 8
diving deeper to 9 meters...
calculated depth: 9
diving deeper to 10 meters...
calculated depth: 10
PS C:\> & { Test-Diving -Depth 1 }
diving deeper to 1 meters...
calculated depth: 2
diving deeper to 2 meters...
calculated depth: 3
diving deeper to 3 meters...
calculated depth: 4
diving deeper to 4 meters...
calculated depth: 5
diving deeper to 5 meters...
calculated depth: 6
diving deeper to 6 meters...
calculated depth: 7
diving deeper to 7 meters...
calculated depth: 8
diving deeper to 8 meters...
calculated depth: 9
diving deeper to 9 meters...
calculated depth: 10
diving deeper to 10 meters...
calculated depth: 11
PS C:\>
Test-NestLevel总会返回从当前代码的作用域到全局作用域的嵌套深度。
