function - 不能在函数中调用管道属性。电源外壳

Question

所以我正在尝试创建一个“下载”函数，该函数使用管道对象属性来确定下载方法(sftp 或 http)。然后为 putty/winscp 创建一个 sftp 脚本或 curl http url。我定义对象如下:

#WinSCP
$winscp = new-object psobject            
$winscp | add-member noteproperty name "WinSCP"
$winscp | add-member noteproperty dltype "http"
$winscp | add-member noteproperty file "winscp.exe"
$winscp | add-member noteproperty url "https://cdn.winscp.net/files/WinSCP-5.17.8-Setup.exe"
$winscp | add-member noteproperty path "$env:ProgramFiles(x86)\WinSCP"
$winscp | add-member noteproperty install 'msiexec /i "$DataPath\$winscp.file" /quiet /norestart'

#Database
$db = new-object psobject            
$db | add-member noteproperty name "Client Database"
$db | add-member noteproperty dltype "sftp"
$db | add-member noteproperty file "database_"
$db | add-member noteproperty ver "check"
$db | add-member noteproperty ext ".csv"
$db | add-member noteproperty dir "db"

#DatabaseVersion
$db_ver = new-object psobject            
$db_ver | add-member noteproperty name "Database Version File"
$db_ver | add-member noteproperty dltype "sftp"
$db_ver | add-member noteproperty file "current_version.txt"
$db_ver | add-member noteproperty dir "db"

目前，函数中的 $Input 变量有问题。它只能使用一次并且不会转换为 if 语句。由于它包含一个具有多个属性的对象，因此我认为首先需要在函数内将其转换为一个新对象。我是 powershell 的新手，还没有找到这样做的方法。这是我制作并尝试使用的功能:

function Download () {

    #HTTP Download Method
    if ($input.dltype -eq "http") {
        curl $input.url -O $DataPath\$input.file
        #HTTP Success or Error
        $curlResult = $LastExitCode
        if ($curlResult -eq 0)
        {
          Write-Host "Successfully downloaded $input.name"
        }
        else
        {
          Write-Host "Error downloading $input.name"
        }
        pause
}

    #SFTP Download Method
    if ($input.dltype -eq "sftp") {
        sftpPassCheck
        #Detect if version required
        if ($input.ver = "check") {
        #Download the objects version file
        "$+$Input+_ver" | Download
        #Update the object's ver property
        $input.ver = [IO.File]::ReadAllText("$DataPath\current_version.txt")
        #Build the new filename
        $input.file = "$input.file"+"$input.ver"+"$input.ext"
        #Delete the version file
        Remove-Item "$DataPath\current_version.txt"
        }
        & "C:\Program Files (x86)\WinSCP\WinSCP.com" `
         /log="$DataPath\SFTP.log" /ini=nul `
         /command `
            "open sftp://ftpconnector:$script:sftp_pass@$input.ip/ -hostkey=`"`"ssh-ed25519 255 SETvoRlAT0/eJJpRhRRpBO5vLfrhm5L1mRrMkOiPS70=`"`" -rawsettings ProxyPort=0" `
            "cd /$input.dir" `
            "lcd $DataPath" `
            "get $input.file" `
            "exit"
        #SFTP Success or Error
        $winscpResult = $LastExitCode
        if ($winscpResult -eq 0)
        {
          Write-Host "Successfully downloaded $input.name"
        }
        else
        {
          Write-Host "Error downloading $input.name"
        }
    }
}

我可能遗漏了一些简单的东西，但我现在一无所知。哦用法应该是:

WinSCP | download

Answer 1

将来自管道的输入绑定(bind)到函数的参数的正确方法是声明一个高级函数 - 参见about_Functions_Advanced_Parameters以及此答案底部的实现。

但是，在简单的情况下，一个过滤器就可以了，它是一种函数的简化形式，它将管道输入隐式绑定(bind)到 automatic $_ variable并为每个输入对象调用:

filter Download {
  if ($_.dltype -eq "http") { 
    # ...
  }
}

$input is another automatic variable ，在简单(非高级)函数中，它是所有管道输入的枚举器 被接收，因此必须循环。

也就是说，下面的simple function 等价于上面的filter:

function Download {
  # Explicit looping over $input is required.
  foreach ($obj in $input) {
    if ($obj.dltype -eq "http") { 
      # ...
    }
  }
}

---

如果您确实想将它变成一个高级函数(请注意，我已经更改了名称以符合 PowerShell 的动词-名词命名约定):

function Invoke-Download {

  param(
    # Declare a parameter explicitly and mark it as
    # as pipeline-binding.
    [Parameter(ValueFromPipeline, Mandatory)]
    $InputObject  # Not type-constraining the parameter implies [object]
  )

  # The `process` block is called for each pipeline input object
  # with $InputObject referencing the object at hand.
  process {

    if ($InputObject.dltype -eq "http") { 
      # ...
    }

  }

}