CODEWITHSUNDEEP
powershellazure-devops
JDH
JDH

Reputation: 2812

Detect an array of empty objects

I'm calling the VSTS Pull Request Query documented here: https://learn.microsoft.com/en-us/rest/api/vsts/git/pull%20request%20query/get?view=vsts-rest-4.1

It returns an object array of results. I wanted to detect when no results are returned and react accordingly. I thought I could check the response.results.length, but it will be 1 even if there are no results. It returns an array of 1 empty object. I'm having a hard time detecting that condition. The one solution I thought of is: 

    if(($pullRequests.results | Get-Member -MemberType Properties).Length -eq 0){some code}

Since a vanilla ps object has 4 members and the populated object has an additional note property it will work. My method seems hackish, is there a better approach?

I tried checking length, exists, and bool:


    PS> $pullRequests.results[0].Length
    1
    PS> $temp = $pullRequests.results[0]
    PS> $temp | Get-Member

    TypeName: System.Management.Automation.PSCustomObject

    Name        MemberType Definition
    ----        ---------- ----------
    Equals      Method     bool Equals(System.Object obj)
    GetHashCode Method     int GetHashCode()
    GetType     Method     type GetType()
    ToString    Method     string ToString()

    PS> $temp -eq $null
    False
    PS> if($temp){"YAY"}else{"BOO"}
    YAY

Upvotes: 0

Views: 2098

Answers (2)

Bruce Payette
Bruce Payette

Reputation: 2629

This does sound like a bug in the API. As a work around, checking for properties (as opposed to members which also includes methods) seems like the right approach. The easiest way to do this ix as follows:

if ($pullRequests.PSObject.Properties)
{
    "Object has properties so process it."
}
else
{
    "Object has no properties, ignore it."
}

Upvotes: 1

Adam
Adam

Reputation: 4168

Oh man, that stinks.

Lemme make sure I understand your problem. You're expecting an object that looks something like the following when data is returned:

$full_collection_ps_objects = `
    @([PSCustomObject]@{a=1;b=2}, [PSCustomObject]@{a=1;b=3})

A collection of psobjects.

When no data is returned, you get an array of objects with a single empty psobject:

$empty_collection_ps_objects = @([PSCustomObject]@{})

I think you nailed it. Property count is a good indicator. I'm a little neurotic. That might lead me to get paranoid that another default property might appear at some later point. I might consider looking for specific field name, a primary key of sorts with something like:

if( $($empty_collection_ps_objects | Get-Member).Name -contains 'a' ) { $true }
if( $($full_collection_ps_objects | Get-Member).Name -contains 'a' ) { $true }

Upvotes: 0

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