Timers.Timer瘫痪脚本

Question

我正在尝试运行这示例：

Clear-Host
$timer = [Timers.Timer]::new()
$timer.Interval = 200
$action = {
    if($complete -eq 8){
        write-host "completed $complete" -ForegroundColor Red
        write-host "Timer stopped" -ForegroundColor Red
        $timer.stop()
        Unregister-Event thetimer
    }
}
Register-ObjectEvent -InputObject $timer -EventName elapsed `
–SourceIdentifier  thetimer -Action $action

$complete = 0
$timer.Start()

while($true){
    Write-Host "Script working: $complete" -ForegroundColor Green
    Start-Sleep -m 400
    $complete++
}

但是当计时器停止时，脚本就瘫痪了。

我做错了什么，怎么解决？

Answer 1

• 除非您在全局范围内直接执行它(通过在提示符处粘贴它，或者通过点源包含它的脚本)，否则您的代码根本无法正常工作。

- The reason is that **a script block passed to** [**`Register-ObjectEvent`**](https://learn.microsoft.com/powershell/module/microsoft.powershell.utility/register-objectevent)**'s** **`-Action`** **parameter runs inside a** _**dynamic module**_**, which sees only the** _**global**_ **scope's variables, not that of any other caller**, such as a script's.

• 如果您确实从全局范围运行，则-Action 挂起是由在脚本块中调用 注销-事件 引起的。

- **Call it from the** _**caller's scope**_ **instead** (i.e. from the same scope where `Register-ObjectEvent` was called).

- That the code _hangs_ when called from inside the `-Action` script block (happens up to at least PowerShell 7.1, the version current as of this writing) should be considered a _bug_; it seems to occur when _more events are pending_ at the time `Unregister-Event` is called; the problem has been reported in [GitHub issue #16154](https://github.com/PowerShell/PowerShell/issues/16154)

下面是一个自包含的工作示例，您也可以从脚本中调用该示例：

$timer = [Timers.Timer]::new()
$timer.Interval = 200

$action = {
  # Note: This script block generally does NOT see the caller's variables.
  # Refer to the originating timer object with $Event.Sender or $args[0]
  $timer = $Event.Sender
  # Get the variable object passed to -MessageData, via $Event.MessageData
  $counter = $Event.MessageData.Value
  # Note: Since you're only *getting* an *integer* value, you needn't worry
  #       about thread synchronization.
  if ($timer.Enabled -and $counter -ge 8) { 
      write-host "completed $counter" -ForegroundColor Red
      write-host "Timer stopped" -ForegroundColor Red
      $timer.stop()
      # Do NOT try to call Unregister-Event here - it'll cause a hang.
  }
}

# Initialize the counter variable.
$complete = 0

# Get the variable as a variable *object* that can be passed to the -Action
# script block with -MessageData.
$counterVarObject = Get-Variable complete

# Register the event and pass the variable object with -MessageData.
$evtJob = Register-ObjectEvent -InputObject $timer -EventName elapsed `
                               –SourceIdentifier thetimer `
                               -Action $action -MessageData $counterVarObject

$timer.Start()

try {
  while ($timer.Enabled) { # Loop until the timer stops.
      Write-Host "Script working: $complete" -ForegroundColor Green
      Start-Sleep -MilliSeconds 400
      $complete++
  }
}
finally { # This is called even if the loop is aborted with Ctrl-C.
  # Remove the event job, which also unregisters the event.
  $evtJob | Remove-Job -Force
}