Laravel Nova BelongsTo field has error when using with $request->viaResource

Question

• Laravel Version: 5.8
• Nova Version: 2.0.5
• PHP Version: 7.3
• Operating System and Version: MAC OS 10.14.4
• Browser type and version: Google Chrome 75.0.3770.100

Description:

I have an application allows creating a task. A task belongs to a campaign.

I have a creating button in campaign detail page, if user click that button, then the URL will be like this: http://demo.test/nova/resources/tasks/new?viaResource=campaigns&viaResourceId=1&viaRelationship= .

As you can see, I added the resource id , so I can use them when creating a task. Something like that:

$campaign = Campaign::find($request->viaResourceId);
...
Select::make('Campaign', 'campaign_id')
                ->options([$campaign->id => $campaign->name])
                ->displayUsingLabels()
                ->withMeta(['value' => $campaign->id])
                ->hideWhenUpdating()
                ->readonly(true),

That code works unless I use a BelongsTo field for another relationship (in this case is task group). It seems the BelongsTo field made another request, and it didn't attach the viaResourceId in the URL so I coud not access my campaign variable. For example, $campaign->id -> I got the error: Trying to get property 'id' of non-object

Answer 1

Change app\\Nova\\Task.php in fields part, to this:

public function fields(Request $request)
{
    if($request->editMode=="create" && !empty($request->viaResource) && !empty($request->viaResourceId)){
        $campaign = Campaign::find($request->viaResourceId);
        return [
            ID::make()->sortable(),
            Text::make('Name')->sortable(),
            Select::make('Campaign', 'campaign_id')
                ->options([$campaign->id => $campaign->name])
                ->displayUsingLabels()
                ->withMeta(['value' => $campaign->id])
                ->hideWhenUpdating()
                ->readonly(true),
            BelongsTo::make('Group')->display('name'),
        ];
    }
    return [
        ID::make()->sortable(),
        Text::make('Name')->sortable(),
        BelongsTo::make('Campaign')->display('name'),
        BelongsTo::make('Group')->display('name'),
    ];
}

I checked it in my nova draft project, it runs well, not any error!