Why does the definition $id = 1 need?

Question

I try to customize my profile on Windows PowerShell.

Referring a book, I wrote the following code in Microsoft.Powershell_profile.ps1.

function Prompt
{
    $id = 1
    $historyItem = Get-History -Count 1
    if($historyItem)
    {
        $id = $historyItem.Id +1
    }

    Write-Host -ForegroundColor DarkGray "`n[$(Get-Location)]"
    Write-Host -NoNewLine "PS:$id > "
    $host.UI.RawUI.WindowTitle = "$(Get-Location)"
    "`b"
}

I can understand most of how the code works, but not understand the $id = 1 (line 3).

Why does it need this code? $id is defined in line 7, so $id = 1 isn't need here, is it?

So, I try to execute this code and the without $id = 1 code. To me, there's no difference.

Why is $id = 1 added to this code?

Answer 1

It isn't required. The code you posted needs it because it needlessly distinguishes between "has history" and "doesn't have history". If you removed the line $id = 1 and started a new PowerShell instance you'd have an empty $id as long as the command history remains empty.

You could get the same result as the code from your question by simply running

$id = (Get-History -Count 1).Id + 1

because (Get-History -Count 1).Id evaluates to an empty result if the history is empty, which is automatically cast to 0 for the addition operation.

Answer 2

I just want to point out that it can also be written in a more terse way like this:

$id = if($historyItem) { $historyItem.Id +1 } else { 1 }

Answer 3

try like this

1. declare a final int currentIndex;
2. declare a constructor for your class yourclass({ this.currentIndex = 0 }); 0 is for first page
3. navigate like yourclass(currentIndex: 0));