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powershellstring-formatting

Parsing a Powershell variable

You have all been a great help - let me start by saying that.

I get the below output from a function I run - the data is stored in a variable called $response, obtained from an Invoke-RestMethod call.

@{ResourceType=UserStory; Id=202847; Name=Professional Lines: 2,800,000 Policy Aggregate Limit update}

How do i go about parsing these values into new variables so the end result is 

TP Id:202847 Professional Lines: 2,800,000 Policy Aggregate Limit update
Solution

  • What you're showing is the stringified form of a custom object, which uses a hashtable-like textual representation.

    That custom object's definition looks something like this:

    # Construct a custom object with .ResourceType, .Id, and .Name properties.
$response = [pscustomobject] @{
  ResourceType = 'UserStory'
  Id = 202847
  Name = 'Professional Lines: 2,800,000 Policy Aggregate Limit update'
}

    If you include this variable in an expandable string (interpolating string), you'll get the representation in your question[1] - note that you'll get the same representation if you pass the object to the Write-Host cmdlet[2], as well as even with default output formatting if [pscustomobject] instances are nested in property values:

    # Note the enclosing "..."
PS> "$response"

@{ResourceType=UserStory; Id=202847; Name=Professional Lines: 2,800,000 Policy Aggregate Limit update}

# Custom object nested in a property value:
PS> [pscustomobject] @{ foo = [pscustomobject] @{ bar = 'baz' } }

foo
---
@{bar=baz}

    Note that without the enclosing "...", you'd get a nicer, tabular representation, courtesy of PowerShell's output-formatting system.

    PS> $response  # direct output of the object

ResourceType     Id Name
------------     -- ----
UserStory    202847 Professional Lines: 2,800,000 Policy Aggregate Limit update

    Assuming $response is actually still a custom object, and not a string representation of it, you can simply access the custom object's properties to build your string, again using an expandable string:

    PS> "TP Id:$($response.Id) $($response.Name)"
TP Id:202847 Professional Lines: 2,800,000 Policy Aggregate Limit update

    Note the need to use $(...) around the property references - see this answer for a summary of PowerShell's string-expansion rules.

    An alternative approach is to use the -f operator, which uses formatting strings like the .NET String.Format() method:

    PS> 'TP ID:{0} {1}' -f $response.Id, $response.Name
TP ID:202847 Professional Lines: 2,800,000 Policy Aggregate Limit update

    [1] You can also obtain this representation by calling .psobject.ToString() on a custom object; curiously, just .ToString() doesn't work, as of PowerShell Core 6.1.0; this surprising discrepancy is discussed in this GitHub issue.

    [2] Do note that Write-Host's purpose is to provide for-display-only (to-host) output, which bypasses PowerShell's success output stream, and thereby the ability to capture or redirect its output - see this answer for more information.