Laravel model with custom generated id - laravel

Question

In my Demande model, for the ID I have not used the default incremental id, not even the ulid. I have customized the generation of the id. But the issue is that when you call it in route, that id is not recognized and the item cannot be found.
The snippet of my model is :
class Demande extends Model
{
protected static function boot()
{
parent::boot();
static::creating(function (Demande $demande) {
$demande->id = self::generateCode($demande->matricule);
});
}
}
Where the generateCode() function is :
public static function generateCode(string $matricule): string
{
// {$this->matricule}-{increment} for example: 2021020061-01
// make sure the code is unique
$count = self::where('matricule', $matricule)->count() + 1;
return $matricule . Str::padLeft($count, 2, '0');
}
With the snippet of the route call :
Route::resource('demandes', DemandeController::class);
In DemandeController, if i do this in the show function :
public function show(Demande $demande)
{
$title = $demande->code;
$etudiant = $demande->etudiant;
....
return view('admin.demandes.show', compact('demande', 'title', 'etudiant'));
}
This throws an error that $demande object is not found. And I am oblidged to change into :
public function show($demande)
{
$demande = Demande::find($demande);
$title = $demande->code;
$etudiant = $demande->etudiant;
....
return view('admin.demandes.show', compact('demande', 'title', 'etudiant'));
}
where I get that $demande param as ID and manually do the find.
Is there a setting inside Demande model or anywhere that needs to be set so that the custom generated id be recognized ?