Question

我已获得以下代码：

function f()
{
    begin{$count=0}
    process{$count+=10}
    end{$count}
}
1..10|f # OK
1..10|%{
    begin{$count=0}
    process{$count+=10}
    end{$count}
} # Error

第一个＆＃34; f＆＃34;调用成功，而％{}块显示错误：

100
% : The script block cannot be invoked because it contains more than one clause. The Invoke() method can only be used on script blocks that contain a single clause.
At D:\Untitled1.ps1:13 char:7
+ 1..10|%{
+       ~~
    + CategoryInfo          : InvalidOperation: (:) [ForEach-Object], PSInvalidOperationException
    + FullyQualifiedErrorId : InvalidOperation,Microsoft.PowerShell.Commands.ForEachObjectCommand

但为什么呢？ ForEach-Object不支持begin / process / end块？

Answer 1

1..10 |ForEach-Object -Begin {$count=0} -Process {$count+=10} -End {$count}将各个块作为单独的命名参数。

在你的情况下，那将是：

-Begin <ScriptBlock>
    Specifies a script block that runs before processing any input objects.

    Required?                    false
    Position?                    named
    Default value                None
    Accept pipeline input?       false
    Accept wildcard characters?  false


-End <ScriptBlock>
    Specifies a script block that runs after processing all input objects.

    Required?                    false
    Position?                    named
    Default value                None
    Accept pipeline input?       false
    Accept wildcard characters?  false

<# ... #>

-Process <ScriptBlock[]>
    Specifies the operation that is performed on each input object. Enter a script
    block that describes the operation.

    Required?                    true
    Position?                    1
    Default value                None
    Accept pipeline input?       false
    Accept wildcard characters?  false

帮助文件中有详细记录 - 来自Get-Help ForEach-Object -Parameter *：

student

Answer 2

作为附录，如果您希望构建代码以便于阅读，那么这只是一个小问题。延续时间刻度（＆＃34;`＆＃34;）很重要 - 因为我刚刚发现了自己的一些费用！

Get-Content -Path $SelectedFiles | ForEach-Object `
-Begin {
 #- Do Begin stuff -----
 } `
-Process {
#- Do Process stuff
} `
-End {
#- Do End stuff
}
#- EndOf: ForEach is here -----
#- NB! Continuation tick "`" must be preceded by space & be LAST character on line!!!!!

要在ISE中提供帮助，在正确识别时，参数（Begin，Process，End）的颜色应与其他参数（我的参数为黑色）相同。在ISE中使用上面的代码，在打勾后放置一个空格，在打勾之前没有空格等。我没有意识到“空间”的重要性。可能 - 咧嘴笑！祝好运！希望这有助于像我这样的另一个初学者。

Answer 3

一件很酷的事情是，您可以在不指定参数的情况下进行操作，并且可以通过使用-process和-remainingscripts在幕后实现。

1..10 | ForEach {$count=0} {$count+=10} {$count}

100

我不能在ForEach-Object中使用begin / process / end块？

3 个答案: