It is the weekend, and there’s no vacation to disturb my leisure. The Scripting Wife is planning on heading over to her friend’s house for some kind of party. I did not bother to ask if I was invited for fear that I might actually be expected to make an appearance. Therefore, after a quick breakfast, with teapot in hand I made a beeline to my office. <\/p>\n
Windows PowerShell 2.0 introduced many new cmdlets, but the changes were extended under the covers as well. One such addition is the GetNewClosure<\/strong> method from the ScriptBlock<\/strong> class. A script block in Windows PowerShell is code inside curly brackets. The If<\/strong> statement, foreach<\/strong> statement, switch<\/strong> statement, and functions all use script blocks. But it can be easier than that to create. Here, for example is a very simple script block. <\/p>\n PS C:\\> {“hi”} | gm You will notice that when you have the curly brackets, you have an instance of a System.Management.Automation.ScriptBlock<\/strong> .NET Framework class, and the members of that class are available to you. One of the methods is the GetNewClosure<\/strong> method. But what does it actually do?<\/p>\n The easiest way to figure out what the GetNewClosure<\/strong> method does is to illustrate it with a bit of code. The first code will run without the GetNewClosure<\/strong>, and the second run will be with the GetNewClosure<\/strong>. <\/p>\n Get-WithoutNewClosure.ps1<\/strong><\/p>\n function Test-Function ([int]$x) When the script is run, the following output is displayed:<\/p>\n PS C:\\Users\\ed.NWTRADERS> C:\\data\\ScriptingGuys\\2010\\HSG_7_5_10\\Get-WithoutNewClosure.ps1 Before running the script, it is important to set the $DebugPreference<\/strong> variable to “continue”<\/strong> as shown here:<\/p>\n $DebugPreference = “continue”<\/span><\/p>\n What happens is the Test-Function<\/strong> function returns a script block. Inside the script block, the variables $x<\/strong> and $y<\/strong> do not have any value. When the $m2<\/strong> and $m5<\/strong> variables are invoked, the script block code that was returned the first time is executed. The value of $x<\/strong> is still null, but the value of $y<\/strong> contains the value that was passed to it. This is shown here:<\/p>\n DEBUG: Invoke &$m2 and pass vlaue of 3 When the GetNewClosure<\/strong> method is added to the script block, the value that was passed the first time the Test-Function<\/strong> was called is retained. The Get-WithNewClosure.ps1 script is shown here.<\/p>\n Get-WithNewClosure.ps1<\/strong><\/p>\n function Test-Function ([int]$x) The results of running the script are shown here:<\/p>\n PS C:\\Users\\ed.NWTRADERS> C:\\data\\ScriptingGuys\\2010\\HSG_7_5_10\\Get-WithNewClosure.ps1 When the GetNewClosure<\/strong> method is added to the script block, it causes the script block to remember the values that were passed the first time. This is shown here:<\/p>\n DEBUG: Invoke &$m2 and pass vlaue of 3 The following image shows the Windows PowerShell ISE after the Get-WithNewClosure.ps1 script has run.<\/p>\n <\/a><\/p>\n This technique can be really useful when creating functions that contain other script blocks. For example, it could be useful when writing a function that creates another function on the fly. In addition, it can solve problems that in Windows PowerShell 1.0 necessitated polluting the global variable namespace. <\/p>\n If you want to know exactly what we will be looking at tomorrow, follow us on Twitter<\/a> or Facebook<\/a>. If you have any questions, send e-mail to us at scripter@microsoft.com<\/a>, or post your questions on the Official Scripting Guys Forum<\/a>. See you tomorrow. Until then, peace.<\/p>\n <\/p>\n Ed Wilson and Craig Liebendorfer, Scripting Guys<\/strong><\/p>\n Microsoft Scripting Guy Ed Wilson here. The first weekend after vacation—ah! During my one-on-one meeting with my manager this past week, Steve asked me, “How is it going?” I replied, “I need a vacation from my vacation.” That tends to be the rule with me rather than the exception. I seldom get to vacate […]<\/p>\n","protected":false},"author":595,"featured_media":87096,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[3,4,134,61,45],"class_list":["post-17801","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-scripting","tag-scripting-guy","tag-scripting-techniques","tag-troubleshooting","tag-weekend-scripter","tag-windows-powershell"],"acf":[],"blog_post_summary":" Microsoft Scripting Guy Ed Wilson here. The first weekend after vacation—ah! During my one-on-one meeting with my manager this past week, Steve asked me, “How is it going?” I replied, “I need a vacation from my vacation.” That tends to be the rule with me rather than the exception. I seldom get to vacate […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/17801","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/users\/595"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/comments?post=17801"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/posts\/17801\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/media\/87096"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/media?parent=17801"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/categories?post=17801"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/scripting\/wp-json\/wp\/v2\/tags?post=17801"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
TypeName: System.Management.Automation.ScriptBlock
Name MemberType Definition
—- ———- ———-
Equals Method bool Equals(System.Object obj)
GetHashCode Method int GetHashCode()
GetNewClosure Method scriptblock GetNewClosure()
GetPowerShell Method powershell GetPowerShell(Params System.Object[] a…
GetSteppablePipeline Method System.Management.Automation.SteppablePipeline Ge…
GetType Method type GetType()
Invoke Method System.Collections.ObjectModel.Collection[psobjec…
InvokeReturnAsIs Method System.Object InvokeReturnAsIs(Params System.Obje…
ToString Method string ToString()
Attributes Property System.Collections.Generic.List`1[[System.Attribu…
File Property System.String File {get;}
IsFilter Property System.Boolean IsFilter {get;set;}
Module Property System.Management.Automation.PSModuleInfo Module …
StartPosition Property System.Management.Automation.PSToken StartPositio…
PS C:\\><\/span><\/p>\n
{
Write-Debug “In Function value of `$x $x”
Return {
param([int]$y) $y + $x
write-debug “In Script Block `$x $x `$y $y”}
}
Write-Debug “Preparing to call test-function and pass value of 2”
$m2 = Test-Function 2
write-debug “The value of `$m2 after call function $m2. The value of `$x $x `$y $y”
Write-Debug “Preparing to call test-function and pass value of 5”
$m5 = Test-Function 5
Write-debug “The value of `$m5 after call function $m5. The value of `$x $x `$y $y”
Write-Debug “Invoke `&`$m2 and pass vlaue of 3”
&$m2 3 #expected: 5 actual: 3
Write-debug “After invoke `&`$m2 and pass value of 3 `$x equals $x `$y equals $y”
Write-debug “Invoke `&`$m5 and pass value of 6”
&$m5 6 #expected: 11 actual: 6
Write-debug “After invoke `&`$m5 and pass value of 6 `$x equals $x `$y equals $y”<\/span><\/p>\n
DEBUG: Preparing to call test-function and pass value of 2
DEBUG: In Function value of $x 2
DEBUG: The value of $m2 after call function
param([int]$y)
$y + $x
write-debug “In Script Block `$x $x `$y $y”. The value of $x $y
DEBUG: Preparing to call test-function and pass value of 5
DEBUG: In Function value of $x 5
DEBUG: The value of $m5 after call function
param([int]$y)
$y + $x
write-debug “In Script Block `$x $x `$y $y”. The value of $x $y
DEBUG: Invoke &$m2 and pass vlaue of 3
3
DEBUG: In Script Block $x $y 3
DEBUG: After invoke &$m2 and pass value of 3 $x equals $y equals
DEBUG: Invoke &$m5 and pass value of 6
6
DEBUG: In Script Block $x $y 6
DEBUG: After invoke &$m5 and pass value of 6 $x equals $y equals<\/span><\/p>\n
3
DEBUG: In Script Block $x $y 3
DEBUG: After invoke &$m2 and pass value of 3 $x equals $y equals
DEBUG: Invoke &$m5 and pass value of 6
6
DEBUG: In Script Block $x $y 6
DEBUG: After invoke &$m5 and pass value of 6 $x equals $y equals<\/span><\/p>\n
{
Write-Debug “In Function value of `$x $x”
Return {
param([int]$y) $y + $x
write-debug “In Script Block `$x $x `$y $y”}.GetNewClosure()
}
Write-Debug “Preparing to call test-function and pass value of 2”
$m2 = Test-Function 2
write-debug “The value of `$m2 after call function $m2. The value of `$x $x `$y $y”
Write-Debug “Preparing to call test-function and pass value of 5”
$m5 = Test-Function 5
Write-debug “The value of `$m5 after call function $m5. The value of `$x $x `$y $y”
Write-Debug “Invoke `&`$m2 and pass vlaue of 3”
&$m2 3 #expected: 5 actual: 3
Write-debug “After invoke `&`$m2 and pass value of 3 `$x equals $x `$y equals $y”
Write-debug “Invoke `&`$m5 and pass value of 6”
&$m5 6 #expected: 11 actual: 6
Write-debug “After invoke `&`$m5 and pass value of 6 `$x equals $x `$y equals $y”<\/span><\/p>\n
DEBUG: Preparing to call test-function and pass value of 2
DEBUG: In Function value of $x 2
DEBUG: The value of $m2 after call function
param([int]$y)
$y + $x
write-debug “In Script Block `$x $x `$y $y”. The value of $x $y
DEBUG: Preparing to call test-function and pass value of 5
DEBUG: In Function value of $x 5
DEBUG: The value of $m5 after call function
param([int]$y)
$y + $x
write-debug “In Script Block `$x $x `$y $y”. The value of $x $y
DEBUG: Invoke &$m2 and pass vlaue of 3
5
DEBUG: In Script Block $x 2 $y 3
DEBUG: After invoke &$m2 and pass value of 3 $x equals $y equals
DEBUG: Invoke &$m5 and pass value of 6
11
DEBUG: In Script Block $x 5 $y 6
DEBUG: After invoke &$m5 and pass value of 6 $x equals $y equals<\/span><\/p>\n
5
DEBUG: In Script Block $x 2 $y 3
DEBUG: After invoke &$m2 and pass value of 3 $x equals $y equals
DEBUG: Invoke &$m5 and pass value of 6
11
DEBUG: In Script Block $x 5 $y 6
DEBUG: After invoke &$m5 and pass value of 6 $x equals $y equals<\/span><\/p>\n![\"Image](\"http:\/\/img.microsoft.com\/library\/media\/1033\/technet\/images\/scriptcenter\/qanda\/hsg\/2010\/july\/hey0710\/wes-07-10-01-01.jpg\")
<\/p>\n
<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"