delegate.ps1
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############################################ # # Get Delegate # ############################################ function Get-Delegate { <# .SYNOPSIS Create an action[] or func[] delegate for a psmethod reference. .DESCRIPTION Create an action[] or func[] delegate for a psmethod reference. .PARAMETER Method A PSMethod reference to create a delegate for. This parameter accepts pipeline input. .PARAMETER ParameterType An array of types to use for method overload resolution. If there are no overloaded methods then this array will be ignored but a warning will be omitted if the desired parameters were not compatible. .PARAMETER DelegateType The delegate to create for the corresponding method. Example: [string]::format | get-delegate -delegatetype func[int,string] .INPUTS System.Management.Automation.PSMethod, System.Type[] .EXAMPLE $delegate = [string]::format | Get-Delegate string,string Gets a delegate for a matching overload with string,string parameters. It will actually return func<object,string> which is the correct signature for invoking string.format with string,string. .EXAMPLE $delegate = [console]::beep | Get-Delegate @() Gets a delegate for a matching overload with no parameters. .EXAMPLE $delegate = [console]::beep | get-delegate int,int Gets a delegate for a matching overload with @(int,int) parameters. .EXAMPLE $delegate = [string]::format | Get-Delegate -Delegate 'func[string,object,string]' Gets a delegate for an explicit func[]. .EXAMPLE $delegate = [console]::writeline | Get-Delegate -Delegate 'action[int]' Gets a delegate for an explicit action[]. .EXAMPLE $delegate = [string]::isnullorempty | get-delegate For a method with no overloads, we will choose the default method and create a corresponding action/action[] or func[]. #> [CmdletBinding(DefaultParameterSetName="FromParameterType")] [outputtype('System.Action','System.Action[]','System.Func[]')] param( [parameter(mandatory=$true, valuefrompipeline=$true)] [system.management.automation.psmethod]$Method, [parameter(position=0, valuefromremainingarguments=$true, parametersetname="FromParameterType")] [validatenotnull()] [allowemptycollection()] [Alias("types")] [type[]]$ParameterType = @(), [parameter(mandatory=$true, parametersetname="FromDelegate")] [validatenotnull()] [validatescript({ ([delegate].isassignablefrom($_)) })] [type]$DelegateType ) $base = $method.GetType().GetField("baseObject","nonpublic,instance").GetValue($method) if ($base -is [type]) { [type]$baseType = $base [reflection.bindingflags]$flags = "Public,Static" } else { [type]$baseType = $base.GetType() [reflection.bindingflags]$flags = "Public,Instance" } if ($pscmdlet.ParameterSetName -eq "FromDelegate") { write-verbose "Inferring from delegate." if ($DelegateType -eq [action]) { # void action $ParameterType = [type[]]@() } elseif ($DelegateType.IsGenericType) { # get type name $name = $DelegateType.Name # is it [action[]] ? if ($name.StartsWith("Action``")) { $ParameterType = @($DelegateType.GetGenericArguments()) } elseif ($name.StartsWith("Func``")) { # it's a [func[]] $ParameterType = @($DelegateType.GetGenericArguments()) $ParameterType = $ParameterType[0..$($ParameterType.length - 2)] # trim last element (TReturn) } else { throw "Unsupported delegate type: Use Action<> or Func<>." } } } [reflection.methodinfo]$methodInfo = $null if ($Method.OverloadDefinitions.Count -gt 1) { # find best match overload write-verbose "$($method.name) has multiple overloads; finding best match." $finder = [type].getmethod("GetMethodImpl", [reflection.bindingflags]"NonPublic,Instance") write-verbose "base is $($base.gettype())" $methodInfo = $finder.invoke( $baseType, @( $method.Name, $flags, $null, $null, [type[]]$ParameterType, $null ) ) # end invoke } else { # method not overloaded Write-Verbose "$($method.name) is not overloaded." if ($base -is [type]) { $methodInfo = $base.getmethod($method.name, $flags) } else { $methodInfo = $base.gettype().GetMethod($method.name, $flags) } # if parametertype is $null, fill it out; if it's not $null, # override it to correct it if needed, and warn user. if ($pscmdlet.ParameterSetName -eq "FromParameterType") { if ($ParameterType -and ((compare-object $parametertype $methodinfo.GetParameters().parametertype))) { #psv3 write-warning "Method not overloaded: Ignoring provided parameter type(s)." } $ParameterType = $methodInfo.GetParameters().parametertype write-verbose ("Set default parameters to: {0}" -f ($ParameterType -join ",")) } } if (-not $methodInfo) { write-warning "Could not find matching signature for $($method.Name) with $($parametertype.count) parameter(s)." } else { write-verbose "MethodInfo: $methodInfo" # it's important here to use the actual MethodInfo's parameter types, # not the desired types ($parametertype) because they may not match, # e.g. asked for method(int) but match is method(object). if ($pscmdlet.ParameterSetName -eq "FromParameterType") { if ($methodInfo.GetParameters().count -gt 0) { $ParameterType = $methodInfo.GetParameters().ParameterType #psv3 } # need to create corresponding [action[]] or [func[]] if ($methodInfo.ReturnType -eq [void]) { if ($ParameterType.Length -eq 0) { $DelegateType = [action] } else { # action<...> # replace desired with matching overload parameter types #$ParameterType = $methodInfo.GetParameters().ParameterType $DelegateType = ("action[{0}]" -f (($ParameterType|%{"[{0}]" -f $_}) -join ",")) -as [type] } } else { # func<...> # replace desired with matching overload parameter types # need to wrap each type parameter in [ and ] for cases like int[] as "func[int[], int]" is invalid # the correct format is "func[[int[]], [int]]" even though "func[int,int]" is fine. $DelegateType = ("func[{0}]" -f ((($ParameterType + $methodInfo.ReturnType)|% {"[{0}]" -f $_}) -join ",")) -as [type] } } Write-Verbose $DelegateType if ($flags -band [reflection.bindingflags]::Instance) { #$methodInfo.createdelegate($DelegateType, $base) # 4.5 [delegate]::CreateDelegate($delegatetype, $base, $methodInfo, <#throwOnBindFailure:#>$true) } else { [delegate]::CreateDelegate($delegatetype, $methodInfo, <#throwOnBindFailure:#>$true) #$methodInfo.createdelegate($DelegateType) # 4.5 } } } |