powershell - 有条件地替换 PowerShell 对象中的值

Question

我有一个 PSCustomObject 数组包含在一个名为$attendance.

event name date       present
----- ---- ----       -------
A01   Mika 2021-02-22 1
A01   John 2021-02-22 0
B03   Mika 2021-02-24 0
B03   John 2021-02-24 1

列present值必须修改为以下内容：

event name date       present
----- ---- ----       -------
A01   Mika 2021-02-22 Yes
A01   John 2021-02-22 No
B03   Mika 2021-02-24 No
B03   John 2021-02-24 Yes

我可以用一个ForEach-Object循环来改变它，但这会遍历整个对象。

$attendance | 
   ForEach-Object { 
      if ($_.present -eq '1') { $_.present = 'Yes' } else {$_.present = 'No' } 
   }

为了缩短代码，我尝试了以下变体，但无法将其折叠回$attendance变量中。

$attendance.present.replace('1','Yes').replace('0','No')

present是否有使用点符号来更改列值的单行或更简单的方法？

Answer 1

另一种方法可能是Select-Object在此使用：

$attendance | Select-Object *, @{Name = 'present'; Expression = {('No','Yes')[[math]::Sign($_.present)]}} -ExcludeProperty present

输出：

event name date       present
----- ---- ----       -------
A01   Mika 2021-02-22 Yes    
A01   John 2021-02-22 No     
B03   Mika 2021-02-24 No     
B03   John 2021-02-24 Yes

Answer 2

不幸的是，使用点表示法$attendance.present创建了一个新数组，该数组不能用于操作PSCustomObject.

我能想到的最短的：

$attendance.foreach({ $_.present = ('No', 'Yes')[ $_.present ] })

无论present是整数还是字符串，这都有效。当用于索引数组时，PowerShell 会自动将字符串转换为整数。

稍长，使用三元运算符（需要 PS7+）：

$attendance.foreach({ $_.present = $_.present -eq 0 ? 'No' : 'Yes' })

我更喜欢后者，因为我认为它更容易阅读。

Answer 3

I don't know a way to update all the values without using a loop but you can shorten your code to

$attendance | % {$_.present = @('Yes', 'No')[$_.present -eq '0']}

Another option might be to add a custom property doing the conversion

$attendance | 
    Add-Member -Name 'yesno' -MemberType ScriptProperty -Value {
        return  @('Yes', 'No')[$this.present -eq '0']
    }

Example _{Note that my csv delimiter is a comma so change accordingly}

$attendance = @'
event,name,date,present
A01,Mika,2021-02-22,1
A01,John,2021-02-22,0
B03,Mika,2021-02-24,0
B03,John,2021-02-24,1
'@ | ConvertFrom-Csv
$attendance | Add-Member -Name 'yesno' -MemberType ScriptProperty -Value {return  @('Yes', 'No')[$this.present -eq '0']}

$attendance | ft -a

event name date       present yesno
----- ---- ----       ------- -----
A01   Mika 2021-02-22 1       Yes
A01   John 2021-02-22 0       No
B03   Mika 2021-02-24 0       No
B03   John 2021-02-24 1       Yes

Answer 4

By using the Replace() method you're just manipulating the string stored in present, it will not update the value on $attendance, there is no string method to do it either.