Laravel 8 pagination for many to many relation

I have many to many relation for categories and products. In a specific category page I want to add pagination for products.

This is my code in Category model:

public function products() {
    return $this->belongsToMany(Product::class,
        'category_product',
        'category_id',
        'product_id'
    )
    ->where('is_published',1)
    ->orderBy('id','ASC')->paginate(5);
}

This is CategoryController code:

public function show($id) {       
    $category = Category::findorfail($id);        
    return view(category.show, compact('category'); 
}

This is a pagination code in category view blade:

{{ $products->links() }}

This is an error I’m getting:

AppModelsCategory::products must return a relationship instance.

Any solutions?

Answers:

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Method 1

The error message is pretty obvious, The relationship method must return a relationship instance. So these two are gonna work because those return an instance of type IlluminateDatabaseEloquentRelationsBelongsToMany class:

public function products() {
    return $this->belongsToMany(Product::class,
        'category_product',
        'category_id',
        'product_id'
    );
}

// Or

public function products() {
    return $this->belongsToMany(Product::class,
        'category_product',
        'category_id',
        'product_id'
    )
    // This update the internal query of the relationship instance to query the relationship later on.
    ->where('is_published',1)->orderBy('id','ASC');
}

Your code will return an instance of IlluminatePaginationLengthAwarePaginator, which is NOT gonna work:

public function products() {
    return $this->belongsToMany(Product::class,
        'category_product',
        'category_id',
        'product_id'
    )
    ->where('is_published',1)
    ->orderBy('id','ASC')->paginate(5);
}

Then in your controller, you can do something like:

class CategoriesController extends Controller
{
    public function show($id)
    {
        $category = Category::findOrFail($id);
        $products = $category->products()->paginate(5);

        return view('categories.show', compact('category', '$products'));
    }
}

Method 2

Found a solution for this:

CategoryController:

public function show($id) {       
    $category = Category::findorfail($id);
    $category->setRelation('products', $category->products()->paginate(5));
    
    return view(category.show, compact('category'); 
}

View blade:

@foreach($category->products as $product)
    {{ $product->title }}
@endforeach

{!! $category->products->render() !!}

Category model:

public function products() {
    return $this->belongsToMany(Product::class,
        'category_product',
        'category_id',
        'product_id'
    )
    ->where('is_published',1)
    ->orderBy('id','ASC');
}

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0