传递可选参数 [英] Passing an optional parameter

问题描述

我有一个PowerShell脚本CSV2JSON.ps1，其中包含以下代码:

I have a PowerShell script CSV2JSON.ps1 with the following code:

param(
        [String]$FieldSeparator=",",
        [String[]]$Header
)

$input | ConvertFrom-Csv -Delimiter $FieldSeparator -Header $Header | ConvertTo-JSON

如果我将其称为.\CSV2JSON.ps1 -FieldSeparator "|" -Header "name|age"，则可以正常工作.但是，如果删除可选参数Header，则ConvertFrom-Csv cmdlet抱怨Header不能为null:

If I call it as .\CSV2JSON.ps1 -FieldSeparator "|" -Header "name|age" it works fine. However, if I drop the optional parameter Header, the ConvertFrom-Csv cmdlet complains that Header cannot be null:

ConvertFrom-Csv : Cannot validate argument on parameter 'Header'.
The argument is null. Supply a non-null argument and try the command again.

我根本不想传递-Header参数(如果未提供).有没有一种精巧的方法来传递可选参数而无需进入If语句?

I don't want to pass the -Header parameter at all, if it's not provided. Is there a neat way to pass on optional parameters without getting into If statements?

推荐答案

我很惊讶没有人建议

I'm surprised no one has suggested splatting the $PSBoundParameters automatic variable.

$PSBoundParameters 是一个哈希表，其中包含传递给命令的所有参数实参.

$PSBoundParameters is a hashtable containing all the parameter arguments that was passed to the command.

只需将$FieldSeparator参数重命名为$Delimiter，就可以了. 如果需要，可以提供FieldSeparator名称作为参数别名:

Simply rename the $FieldSeparator parameter to $Delimiter and you're good to go. You can provide the FieldSeparator name as a parameter alias if needed:

param(
        [Alias('FieldSeparator')]
        [String]$Delimiter=",",
        [String[]]$Header
)

$input | ConvertFrom-Csv @PSBoundParameters | ConvertTo-JSON

如果在执行调用函数/脚本时省略了-Header参数，则在调用ConvertFrom-Csv

If the -Header parameter is omitted when executing the calling function/script, it'll also be omitted from the call to ConvertFrom-Csv

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