Laravel Filament: sum and count repeater

Question

I'm making a form using filament. I want to count the number of repeater I make, and the sum of the value I input.

I want to make the default value of Total area is the sum of Field area, and the default value of Number of fields is to count the Field I generate. After reading the documentation, I don't think there are such features. But, I just want to make sure if there is a trick to make this happen.

I tried to count($get('fields'), but it thrown an error:

count(): Argument #1 ($value) must be of type Countable|array, null given 

Here's my code:

public static function form(Form $form): Form
    {
        return $form
            ->schema([
                Card::make([
                    Grid::make(2)
                        ->schema([
                            TextInput::make("total_area")
                                ->label("Total area")
                                ->postfix('m²')
                                ->disabled()
                                ->default(fn (Closure $get) => $get('field')),
                            TextInput::make("number_of_field")
                                ->label("Number of fields")
                                ->disabled()
                                ->default(fn (Closure $get) => count($get('fields'))),
                        ]),

                ])->columnSpan(1),

                Card::make([
                    Select::make("measurement_type")
                        ->label("Measurement type")
                        ->required(),

                    Repeater::make('fields')
                        ->label('Field')
                        ->schema([
                            TextInput::make("field")
                                ->label("Field area")
                                ->postfix('m²')
                                ->required(),
                        ])
                ])->columnSpan(1)
            ])->columns(2);
    }

Answer 1

You can use $get variable and get the repeator Property. And you can use the Placeholder props and Set the content to it. Here is the result

public static  function form(Form $form): Form
    {
        return $form
            ->schema([
                Card::make([
                    Grid::make(2)
                        ->schema([
                            Placeholder::make("total_area")
                                ->label("Total area")
                                ->content(function ($get) {
                                    return collect($get('fields'))
                                        ->pluck('field')
                                        ->sum();
                                }),
                            Placeholder::make("number_of_field")
                                ->label("Number of fields")
                                ->content(function ($get) {
                                    return collect($get('fields'))
                                        ->pluck('field')
                                        ->count();
                                })
                        ]),

                ])->columnSpan(1),

                Card::make([
                    Select::make("measurement_type")
                        ->label("Measurement type")
                        ->required(),

                    Repeater::make('fields')
                        ->label('Field')
                        ->schema([
                            TextInput::make("field")
                                ->label("Field area")
                                ->postfix('m²')
                                ->required()
                                ->reactive(),
                        ])
                ])
                    ->reactive()
                    ->columnSpan(1)
            ])->columns(2);
    }