通过动态变量名称获取变量 [英] Get a variable by dynamic variable name

问题描述

如何使用动态便笺属性名称访问从CSV文件导入的数据?也就是说，事先不知道名称.它们确实与模式匹配，并且在脚本运行时从CSV文件中提取.

How does one access data imported from a CSV file by using dynamic note property names? That is, one doesn't know the colunm names beforehand. They do match a pattern and are extracted from the CSV file when the script runs.

例如，考虑一个CSV文件:

As for an example, consider a CSV file:

"Header 1","Header A","Header 3","Header B"
0,0,0,0
1,2,3,4
5,6,7,8

我只想提取以字母结尾的列.为此，我阅读标题行并使用正则表达式提取名称，

I'd like to extract only columns that end with a letter. To do this, I read the header row and extract names with a regex like so,

$reader = new-object IO.StreamReader("C:\tmp\data.csv")
$line = $reader.ReadLine()
$headers = @()

$line.Split(",") | % {
    $m = [regex]::match($_, '("Header [A-Z]")')
    if($m.Success) { $headers += $m.value } }

这将获得我关心的所有列名称:

This will get all the column names I care about:

"Header A"
"Header B"

现在，要访问CSV文件，我将其导入为

Now, to access a CSV file I import it like so,

$csvData = import-csv "C:\tmp\data.csv"

导入CSV将创建一个自定义对象，该对象具有与标题行相同的属性.可以像这样通过NoteProperty名称访问字段，

Import-CSV will create a custom object that has properties as per the header row. One can access the fields by NoteProperty names like so,

$csvData | % { $_."Header A" } # Works fine

这显然需要事先知道列名.我想使用提取并存储到$headers中的colunn名称.我该怎么办?

This obviously requires one to know the column name in advance. I'd like to use colunn names I extracted and stored into the $headers. How would I do that?

到目前为止我已经尝试过的一些事情

Some things I've tried so far

$csvData | % { $_.$headers[0] } # Error: Cannot index into a null array.
$csvData | % { $np = $headers[0]; $_.$np } # Doesn't print anything.
$csvData | % { $_.$($headers[0]) } # Doesn't print anything.

我可以像这样更改脚本，以便它将编写另一个知道列名的脚本.那是我唯一的解决方案吗?

I could change the script like so it will write another a script that does know the column names. Is that my only solution?

推荐答案

我想到的第一件事(也是唯一的一个……对不起)是:

the first thing ( and the only one... sorry) that came in my mind is:

$csvData | % { $_.$(( $csvData | gm | ? { $_.membertype -eq "noteproperty"} )[0].name) }

获取第一个的列值和

$csvData | % { $_.$(( $csvData | gm | ? { $_.membertype -eq "noteproperty"} )[1].name) }

对于第二列，依此类推....

for second column and so on....

这是您需要的吗?

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