如何在脚本块中删除重复的代码

Question

Powershell的新功能。 我正在编写一个脚本，用于监视目录中的文件并将更改报告给控制台。

我

注意到我用于 FS"观察程序"的脚本块中存在相当多的代码重复。

下面是脚本块的片段。 如果需要，我可以发布整个脚本，它有点长，还有更多的事情要做。

# Filter all files
$filter = "*.*"
$watcher = New-Object IO.FileSystemWatcher $watchdir, $filter -Property @{
    IncludeSubdirectories = $true
    EnableRaisingEvents = $true
}
# File creation
Register-ObjectEvent $watcher Created -SourceIdentifier Created -Action {
    $path = $Event.SourceEventArgs.FullPath
    $name = $Event.SourceEventArgs.Name
    $changeType = $Event.SourceEventArgs.ChangeType
    $timeStamp = $Event.TimeGenerated
    $message = "The file '$name' was '$changeType' at '$timeStamp'"
    Write-Host $message
}
# File change
Register-ObjectEvent $watcher Changed -SourceIdentifier Changed -Action {
    $path = $Event.SourceEventArgs.FullPath
    $name = $Event.SourceEventArgs.Name
    $changeType = $Event.SourceEventArgs.ChangeType
    $timeStamp = $Event.TimeGenerated
    $message = "The file '$name' was '$changeType' at '$timeStamp'"
    Write-Host $message
}
# File rename
...
# File delete
...

是否有一种好的模式或更好的方法来编写以减少代码量？

Answer 1

在您的示例中，脚本块完全相同，因此在这种情况下，只需将它们放入变量中并传递即可：

$action = {
    $path = $Event.SourceEventArgs.FullPath
    $name = $Event.SourceEventArgs.Name
    $changeType = $Event.SourceEventArgs.ChangeType
    $timeStamp = $Event.TimeGenerated
    $console_message = "The file '$name' was '$changeType' at '$timeStamp'"
    Write-Host message
}
# File creation
Register-ObjectEvent $watcher Created -SourceIdentifier Created -Action $action
# File change
Register-ObjectEvent $watcher Changed -SourceIdentifier Changed -Action $action

如果您发布一个示例，其中脚本块中存在冗余，但它们并不完全相同，那么展示如何最好地抽象它的示例会更容易。可能没有一个放之四海而皆准的解决方案。

Answer 2

您应该将重用的代码包装到函数中，有关如何执行此操作的说明，请参阅此处： http://windowsitpro.com/windows/create-your-own-powershell-functions

在您的情况下，我将创建以下函数：

function FileChange {
  Register-ObjectEvent $watcher Created -SourceIdentifier Created -Action {
  $path = $Event.SourceEventArgs.FullPath
  $name = $Event.SourceEventArgs.Name
  $changeType = $Event.SourceEventArgs.ChangeType
  $timeStamp = $Event.TimeGenerated
  $console_message = "The file '$name' was '$changeType' at '$timeStamp'"
  Write-Host message
}

然后使用它来替换重复的代码：

# Filter all files
$filter = "*.*"
$watcher = New-Object IO.FileSystemWatcher $watchdir, $filter -Property @{
IncludeSubdirectories = $true
EnableRaisingEvents = $true
}
# File creation
FileChange()
# File change
FileChange()