PowerShell 3 中的成员枚举如何工作? [英] How Does Member Enumeration Work in PowerShell 3?

问题描述

在 PoweShell 2 中，我们做到了:

In PoweShell 2 we did:

Get-ChildItem | ForEach-Object {$_.LastWriteTime} | Sort-Object  

在 Powershell 3 中，我们这样做:

In Powershell 3 we do:

(Get-ChildItem).LastWriteTime | Sort-Object

但是它是如何工作的，我阅读了这篇博客在 MSDN 上发帖，他们说它更快，因为 foreach 循环没有运行?那么它是如何枚举属性的呢?

But how does it work, i read this blog post on MSDN and they say that its faster because the foreach loop isnt running? So how does it enumerate the properties then ?

推荐答案

PowerShell 为我们做了繁重的工作，它在内部循环遍历集合.我喜欢称之为隐式 foreach".假设您指定的成员存在于每个对象上，如果您指定的成员是一个属性，则您将取回其值.如果是方法，则调用每个对象上的方法.

PowerShell is doing the hard work for us and it loops over the collection internally. I like to call this "implicit foreach". Assuming the member you specified is present on each object, if the member you specified is a property, you get back its value. If it's a method, it invokes the method on the each object.

在 v2 中，要获取所有进程名称，您必须自己处理循环:

In v2, to get all process names you had to take care of looping yourself:

Get-Process | Foreach-Object {$_.Name}

在 v3 中，相当于:

In v3, the equivalent would be:

(Get-Process).Name

同样适用于方法.要杀死名称以 note* 开头的所有进程:

Same applies to methods. To kill all processes with name starting with note*:

(Get-Process note*).Kill()

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