{"id":8491,"date":"2014-12-24T06:00:00","date_gmt":"2014-12-24T14:00:00","guid":{"rendered":"http:\/\/www.sapien.com\/blog\/?p=8491"},"modified":"2016-04-08T16:38:45","modified_gmt":"2016-04-08T23:38:45","slug":"find-variables-with-class","status":"publish","type":"post","link":"https:\/\/dev.sapien.com\/blog\/2014\/12\/24\/find-variables-with-class\/","title":{"rendered":"Find variables with class"},"content":{"rendered":"

Follow @juneb_get_help<\/a><\/p>\n

I’ve been playing with the Windows PowerShell 5.0 preview and especially with its new class<\/a> feature. After I create my class, I often create several instances<\/em> of the class and experiment with them in my session. For example, I created a Wine class and then created several instances of my wine class. I saved each Wine instance in a variable.<\/p>\n

$PSWine = [Wine]::new(\"PSCabernet\")\r\n$Shiraz = [Wine]::new()\r\n...<\/pre>\n
After playing with the instances for a while (and enjoying a few sips of PSWine), I couldn’t remember all of the Wine objects that I’d created in my session. They were all in variables, so I used the Get-Variable cmdlet to find the $PSWine variable.<\/p>\n
PS C:\\> Get-Variable \u2013Name PSWine\r\nName\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Value\r\n----\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ------\r\nPSWine\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine<\/pre>\n
Excellent! The value of the variable is the name of the class. This should make it easy to find the other variables.<\/p>\n
PS C:\\> Get-Variable | Where Value \u2013eq \"Wine\"\r\n\r\nName\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Value\r\n----\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -----\r\n?\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 True\r\ntrue\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 True<\/pre>\n
That didn’t work, because the value of the Value property appears to contain “Wine”, but that’s just a display artifact. The Value of the variable is the entire Wine object.<\/p>\n
PS C:\\> (Get-Variable -Name PSWine).Value\r\n\r\nName\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : PSCabernet\r\nWinery\u00a0\u00a0\u00a0\u00a0\u00a0 : Chateau Snover\r\nYear\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 2012\r\nisSparkling : False\r\nColor\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : Red\r\nSweetness\u00a0\u00a0 : VeryDry\r\nDescription : Pithy\r\nRating\u00a0\u00a0\u00a0\u00a0\u00a0 : {96, 94}<\/pre>\n
To get Wine objects in the session, or objects of any particular type, such as strings or integers, call the GetType()<\/strong> method of the value and then take its Name<\/strong> property.<\/p>\n
PS C:\\> Get-Variable | where\u00a0 {$_.value.gettype().Name -eq \"Wine\"}\r\n\r\nName\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Value\r\n----\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -----\r\nDuck\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine\r\n\r\nYou cannot call a method on a null-valued expression.\r\nAt line:1 char:24\r\n+ Get-Variable | where\u00a0 {$_.value.gettype().Name -eq \"Wine\"}\r\n+\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\n+ CategoryInfo\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : InvalidOperation: (:) [], RuntimeException\r\n+ FullyQualifiedErrorId : InvokeMethodOnNull\r\n\r\nPSWine\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine\r\nShiraz\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine<\/pre>\n
Oops! You have to account for variables that don’t have a value. I’ll use the AND<\/strong> operator to make sure that the variable has a value before I try to get the name of its value type. Windows PowerShell has a “lazy” AND<\/strong> operator, which means that if the first part of the AND<\/strong> statement isn’t true, since both parts must be true, it doesn’t even check the second part.<\/p>\n
PS C:\\ps-test> Get-Variable | where {$_.Value -and $_.Value.GetType().Name -eq \"Wine\"}\r\n\r\nName\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Value\r\n----\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -----\r\nDuck\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine\r\nPSWine\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine\r\nShiraz\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Wine<\/pre>\n
It works on all types.<\/p>\n
PS C:\\ps-test> Get-Variable | \r\nwhere {$_.Value -and $_.Value.GetType().Name -eq \"ActionPreference\"}\r\n\r\nName                           Value\r\n----                           -----\r\nErrorActionPreference          Continue\r\nProgressPreference             Continue\r\nWarningPreference              Continue<\/pre>\n
Let’s turn this into a function:<\/p>\n
function Get-VariableOfType ($Type)\r\n{\r\n    Get-Variable | where {$_.Value -and $_.Value.GetType().Name -eq\u00a0 $type}\r\n}<\/pre>\n
Now, back to that Wine glass —\u00a0 I mean class!<\/p>\n
June Blender is a technology evangelist at SAPIEN Technologies, Inc. You can reach her at <\/em>juneb@sapien.com<\/em><\/a> or follow her on Twitter at <\/em>@juneb_get_help<\/em><\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"
Follow @juneb_get_help I’ve been playing with the Windows PowerShell 5.0 preview and especially with its new class feature. After I create my class, I often create several instances of the class and experiment with them in my session. For example, I created a Wine class and then created several instances of my wine class. I […]<\/p>\n","protected":false},"author":31,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[1033,941,25],"tags":[934,28],"class_list":["post-8491","post","type-post","status-publish","format-standard","hentry","category-classes-in-powershell-5-0","category-powershell-5-0","category-windows-powershell","tag-juneb","tag-powershell"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t