代码之家 › 专栏 › 技术社区 › Mark Bertenshaw

从一个函数到另一个函数的内部管道化

powershell

Mark Bertenshaw · 技术社区 · 6 年前

我有一个模块,它有以下两个功能,几乎相同:

<#
    .SYNOPSIS
    Retrieves a VApp from VCloud.
#>
Function Get-VApp
{
    [CmdletBinding()]
    [OutputType([System.Xml.XmlElement])]
    Param(
        [Parameter(Mandatory = $true)]
        [System.Xml.XmlElement] $Session,
        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [string[]] $VAppName
    )
    Begin {
        [System.Xml.XmlElement] $queryList = $Session.GetQueryList();
        [System.Xml.XmlElement[]] $vAppRecords = $queryList.GetVAppsByRecords().VAppRecord;
    }
    Process {
        ForEach ($VAN in $VAppName)
        {
            $vAppRecords |
            Where-Object { $_.name -eq $VAN } |
            ForEach-Object { $_.Get(); }
        }
    }
    End
    {
        #
    }
}

和

<#
    .SYNOPSIS
    Retrieves a VAppRecord from VCloud.
#>
Function Get-VAppRecord
{
    [CmdletBinding()]
    [OutputType([System.Xml.XmlElement])]
    Param(
        [Parameter(Mandatory = $true)]
        [System.Xml.XmlElement] $Session,
        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [string[]] $VAppName
    )
    Begin {
        [System.Xml.XmlElement] $queryList = $Session.GetQueryList();
        [System.Xml.XmlElement[]] $vAppRecords = $queryList.GetVAppsByRecords().VAppRecord;
    }
    Process {
        ForEach ($VAN in $VAppName)
        {
            $vAppRecords |
            Where-Object { $_.name -eq $VAN } |
            ForEach-Object { $_; }
        }
    }
    End
    {
        #
    }
}

本质上,get-vapp与get-vapprecord类似,只是前者对返回的对象调用get()方法。这似乎是浪费。如果我不去管管道,那很容易:

Function Get-VApp
{
        [CmdletBinding()]
        [OutputType([System.Xml.XmlElement])]
        Param(
            [Parameter(Mandatory = $true)]
            [System.Xml.XmlElement] $Session,
            [Parameter(Mandatory = $true)]
            [string[]] $VAppName
        )
    Get-VAppRecord $Session $VAppName |
    ForEach-Object {
        $_.Get();
    }
}

但很明显管道把事情搞砸了。为了提高效率,我不会多次调用begin块中的代码,我希望找到一种不必成批处理记录就可以“很好地”处理管道的方法。

1 回复 | 直到 6 年前

Mark Bertenshaw 6 年前

SteppablePipeline

ProxyCommand.Create()

Get-VAppRecord

$GetVAppRecordCommand = Get-Command Get-VAppRecord
$GetVAppRecordCommandMetadata = [System.Management.Automation.CommandMetadata]::new($GetVAppRecordCommand)

# returns the body of the new proxy functions
[System.Management.Automation.ProxyCommand]::Create($GetVAppRecordCommandMetadata)

Get() process

function Get-VApp {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true, Position=0)]
        [System.Xml.XmlElement]
        ${Session},

        [Parameter(Mandatory=$true, Position=1, ValueFromPipeline=$true)]
        [string[]]
        ${VAppName})

    begin
    {
        try {
            $outBuffer = $null
            if ($PSBoundParameters.TryGetValue('OutBuffer', [ref]$outBuffer))
            {
                $PSBoundParameters['OutBuffer'] = 1
            }
            $wrappedCmd = $ExecutionContext.InvokeCommand.GetCommand('Get-VAppRecord', [System.Management.Automation.CommandTypes]::Function)
            $scriptCmd = {& $wrappedCmd @PSBoundParameters }
            $steppablePipeline = $scriptCmd.GetSteppablePipeline()
            $steppablePipeline.Begin($MyInvocation.ExpectingInput) # Many examples use $PSCmdlet; however setting this ensures that $steppablePipeline.Process() returns the output of the inner function.
        } catch {
            throw
        }
    }

    process
    {
        try {
            $steppablePipeline.Process($_) |ForEach-Object {
                # call Get() on the record
                $_.Get()
            }
        } catch {
            throw
        }
    }

    end
    {
        try {
            $steppablePipeline.End()
        } catch {
            throw
        }
    }
}