How create nested relationship over three models

Hi,

I dont understand the difference between Treatments and Prescriptions.

A Treatment has many products, where each product has a different prescription (amount of intake a user needs).

The prescription can be different for the same product in another treatment.

I hope this clarifies.

An addition: products are shared across treatments. Prescriptions are product/treatment specific.

Why not simply add a column amount in product_treatment pivot (withPivot) ?

Of course! Thanks a lot. I searched to much ;-)

Now I can insert the values into the pivot table: $treatment->products()->updateExistingPivot($product->id, [ 'consumption_interval' => request('consumption_interval'), 'units_per_interval' => request('units_per_interval') ]);

Where I'm still stuck, is accessing the values in the view. The pivot attributes appear fine in the "show" view {{ $product->pivot->units_per_interval }}, but not when editing the attributes. Then the array is missing the pivot relationship. Any idea what I'm missing?

I dont see the diffrence between show and edit about this attribute.

In show I have:

@foreach ($treatment->products as $product)
    $product->pivot->units_per_interval
@endforeach 

Then for the edit view I have the following function in the TreatmentsController, where I pass the treatment and product id in the route Route::get('/treatments/{treatment}/prescription/{product}/edit', 'TreatmentsController@edit_prescription'):

public function edit_prescription(Treatment $treatment, Product $product) {
    return view('prescriptions.edit', compact('product', 'treatment') );
}

But somehow I do not get the attribute in the edit view via $product->pivot->units_per_interval

Not sure of your queries, but looks like in this case it's rather :

$treatment->pivot->units_per_interval

Then I get an error: Trying to get property of non-object.

Do I need to specifically create a query for the single edit view?

Sounds weird, as you need same informations for show and edit.

Yes. The only difference is, in show I access the pivot over the foreach loop and in the edit view I just pass the $product and $treatment object. And both are missing the relationship.

But you edit a treatment that can have many products ?

Yes. Treatment model looks like this:

class Treatment extends Model
{

    protected $fillable = ['name'];

    
    public function user() {

        return $this->belongsTo(User::class);

    }

    public function products() {

        return $this->belongsToMany(Product::class)->withPivot('consumption_interval', 'units_per_interval');
    }

}

And I edit from the treatment controller.

So when you edit a treatment you must eager load all the products and you can access the pivot...

Could you point me to the right direction? Don I do this from the model or the controller?

try to use eager loading with('products.perr')..

In your controller something like that :

$treatment = Treatment::with('products')->find($treatment_id)

and first you should check value availability if not available then print null or something like $products->some->nnnn or 'mesg'

$treatment = Treatment::with('products')->find($treatment_id)

Ok, with this I get the treatment with a collections of two associated products. But in the single edit view I need to additionally filter by product_id. Do I need to chain where clauses?

Could you point me to a direction how I can eager load respecting both foreign keys in the pivot table?

Ok, tried further and found a solution. But could this lines be optimised?

    public function edit_prescription($treatment_id, $product_id) {

        $treatment = Treatment::with(['products' => function ($query) use ($product_id) {
            $query->where('id', '=', $product_id);
        }])->where('treatments.id', $treatment_id)->first();

        $product = $treatment->products->first();
    
        return view('prescriptions.edit', compact('product', 'treatment') );
    }