Do loop using rest api showing unexpected results

Question

I'm adding some results (devices) to an array to then filter and action against later in the script:

$Devurl = "https://my-site.com/internal/api"
$restResults = Invoke-RestMethod -uri "$Devurl/$device" -UseDefaultCredentials -Method Get -ContentType "application/json"

$resultpages = $restResults.Pages
$incpages = ''
$testarray = @()

Do {
    [int]$incpages += 1
    $url = ($restResults.nexturl) -replace 'page=1',"page=$incpages"
    $getresults = Invoke-RestMethod -uri $url -UseDefaultCredentials -Method Get -ContentType "application/json"
    $testarray += $getresults.Models
    $resultpages -= 1
    } while ($resultpages -gt 0)

I can do something like:

$testarray | where {$_.os -like '*windows*'} | select hostname,os

Which works, however I'm puzzled as to why these counts (the total number of devices) are different:

$testarray.Count 
11434

$restResults.Count 
11534

The original $restResults has 116 pages and I've added code to verify the loop increments from page 1 through to page 116.

What am I missing?

Answer 1

It seems like you forgot adding content of first page to the $testarray. When first passing do-while-loop you load the second page by invoking $restResults.nextUrl so the first page gets skipped. I suggest to adjust your script code as follows

$devurl = "https://my-site.com/internal/api";
$restResults = Invoke-RestMethod -Method Get -uri "$devurl/$device" -UseDefaultCredentials;

$resultpages = $restResults.Pages;
$testarray = @();
$testarray += $restResults.Models;

Do {
    $restResults = Invoke-RestMethod -Method Get -uri $restResults.nexturl -UseDefaultCredentials;
    $testarray += $restResults.Models;
    $resultpages -= 1
} while ($resultpages -gt 0)