PowerShell JSON：如何找出密钥是否存在=

xcitsw88 于 2023-11-20 发布在 Shell

关注(0)|答案(2)|浏览(112)

我使用Powershell 5.1，我尝试使用（简单的）JSON文件作为脚本之间的信箱。因此，在脚本的开头，我读取文件，修改它并将其存储在结尾。例如，以下文件

{
    "A":  {
              "April":  "4",
              "August":  "8"
          },
    "J":  {
              "January":  "1",
              "July":  "7"
          }
}

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为了更好的处理，我写了一个Read-Value和一个Write-Value函数。在这个例子中，Read-Value显示了我的问题：函数找不到参数“Name”。

$config_file_full = Join-Path -Path $PSScriptRoot -ChildPath 'months.json'
$config_json = Get-Content -Raw -Path $config_file_full | ConvertFrom-Json

function Read-Value {
    param (
        [string]$Subject,
        [string]$Name
    )
    # $result = $null

    if (-not ($config_json.PSObject.Properties.Name -contains $Subject)) {
        Write-Host "READ NO MATCH for SUBJECT " $Subject
        $result = $null
    } elseif (-not ($config_json.PSObject.Properties.$Subject.Name -contains $Name)) {
        Write-Host "READ NO MATCH FOR SUBJECT " $Subject "NAME " $Name
        $result = $null
    } else {
        $result = $config_json.$Subject.$Name
        Write-Host "READ NO MATCH FOR SUBJECT " $Subject "NAME " $Name "VALUE <" $result ">"
    }

    return $result
}

$a = Read-Value -Subject 'A' -Name 'April'
Write-Host "<" $a ">"

$config_json | ConvertTo-Json | Set-Content -Path $config_file_full

型
结果是

READ NO MATCH FOR SUBJECT  A NAME  April
<  >

型
怎么了？其他条件不符合预期。谢谢

JSON

来源：https://stackoverflow.com/questions/77501024/powershell-json-how-to-find-out-if-key-exists

2条答案

按热度按时间

disbfnqx1#

James Ruskin's answer将解决您的问题，但如果您将if/elseif/else语句替换为两个单独的if块，然后使用return在错误条件下“提前退出”，则可以更优雅地完成此操作：

function Read-Value {
    param (
        [string]$Subject,
        [string]$Name
    )
    if (-not ($config_json.PSObject.Properties.Name -contains $Subject)) {
        Write-Host "READ: No match for SUBJECT '$($Subject)'"
        return
    }

    # if we've reached this point it must mean the subject exists, assign to a variable
    $subjectObject = $config_json.PSObject.Properties[$Subject].Value

    if (-not ($subjectObject.PSObject.Properties.Name -contains $Name)) {
        Write-Host "READ: Matched Subject '$($Subject)' but not Name '$($Name)'"
        return
    }

    Write-Host "READ: Matched Subject '$($Subject)' and Name '$($Name):<$($result)>"
    $config_json.$Subject.$Name
}

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赞(0）回复(0）举报 2023-11-20

4si2a6ki2#

这里有几个问题。

这里的PSObject.Properties是一个PSPropertyInfo示例的集合（感谢@mklement0进行了更正），它不允许您使用点表示法来处理每个属性。
甚至当你到达你想要检查的$Subject时，Name属性包含的是那个Subject的名字，而不是你要检查的$Name。

这应该更好地工作：

function Read-Value {
    param (
        [string]$Subject,
        [string]$Name
    )
    if (-not ($config_json.PSObject.Properties.Name -contains $Subject)) {
        Write-Host "READ: No match for SUBJECT '$($Subject)'"
    } elseif (-not ($config_json.PSObject.Properties[$Subject].Value.PSObject.Properties.Name -contains $Name)) {
        Write-Host "READ: Matched Subject '$($Subject)' but not Name '$($Name)'"
    } else {
        Write-Host "READ: Matched Subject '$($Subject)' and Name '$($Name)': <$($config_json.$Subject.$Name)>"
        $config_json.$Subject.$Name
    }
}

字符串

赞(0）回复(0）举报 2023-11-20

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PowerShell JSON：如何找出密钥是否存在=

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