如何使用"if"管道中的语句 [英] how to use "if" statements inside pipeline

问题描述

我正在尝试在管道内使用if.

I'm trying to use if inside a pipeline.

我知道有where(别名为?)过滤器，但是如果我想仅在满足特定条件的情况下才激活过滤器，该怎么办?

I know that there is where (alias ?) filter, but what if I want activate a filter only if a certain condition is satisfied?

我的意思是，例如:

get-something | ? {$_.someone -eq 'somespecific'} | format-table

如何在管道内使用if来打开/关闭过滤器?是否有可能?有道理吗?

How to use if inside the pipeline to switch the filter on/off? Is it possible? Does it make sense?

谢谢

已编辑以澄清

没有管道，它看起来像这样:

Without pipeline it would look like this:

if($filter) {
 get-something | ? {$_.someone -eq 'somespecific'}
}
else {
 get-something
}

---

在ANSWER的riknik之后进行编辑

显示我正在寻找的傻事示例.您有一个存储在变量$data上的非规范化数据表，并且想要执行一种向下钻取"数据过滤:

Silly example showing what I was looking for. You have a denormalized table of data stored on a variable $data and you want to perform a kind of "drill-down" data filtering:

function datafilter {
param([switch]$ancestor,
    [switch]$parent,
    [switch]$child,
    [string]$myancestor,
    [string]$myparent,
    [string]$mychild,
    [array]$data=[])

$data |
? { (!$ancestor) -or ($_.ancestor -match $myancestor) } |
? { (!$parent) -or ($_.parent -match $myparent) } |
? { (!$child) -or ($_.child -match $mychild) } |

}

例如，如果我只想按特定的父项进行过滤:

For example, if I want to filter by a specific parent only:

datafilter -parent -myparent 'myparent' -data $mydata

这是利用?的非常优雅，高效且简单的方法.尝试使用if做同样的事情，您会明白我的意思.

That's very elegant, performant and simple way to exploit ?. Try to do the same using if and you will understand what I mean.

推荐答案

使用where-object时，条件不必严格与通过管道的对象相关.因此，考虑一种情况，有时我们想过滤奇数个对象，但前提是要满足其他一些条件:

When using where-object, the condition doesn't have to strictly be related to the objects that are passing through the pipeline. So consider a case where sometimes we wanted to filter for odd objects, but only if some other condition was met:

$filter = $true
1..10 | ? { (-not $filter) -or ($_ % 2) }

$filter = $false
1..10 | ? { (-not $filter) -or ($_ % 2) }

您正在寻找的是这种东西吗?

Is this kind of what you are looking for?

这篇关于如何使用"if"管道中的语句的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！