Get next / prev element in Eloquent - php

Question

I have a model for Product and Catalogue. They have many to many relationship, therefore I am using a pivot table called 'items'. I have a route:
/something/something/{catalogue}/{product}
I am passing the product model and catalogue model to the view, which outputs the product information and catalogue information - pretty straight forward. Now I need to have 2 buttons - 'next' and 'previous' to navigate through products in the catalogue.
So one way to do this, I thought I would create 2 methods on the Catalogue model that would accept the current product model and return next / prev model based on ID:
public function prevProduct($product){
$prevProdId = Product::where('id', '<', $product->id)->max('id');
return Product::find($prevProdId);
}
public function nextProduct($product){
$nextProdId = Product::where('id', '>', $product->id)->min('id');
return Product::find($nextProdId);
}
Now this works fine, but as you can see, it retrieves the next product and previous product from the Product table in the database, not the catalogue.
To get all the products in the catalogue, can be done like so: $this->items (on Catalogue model) or $catalogue->items (from view).
I somehow need to get next / prev items from the Catalogue, but can't figure out how. Any suggestions would be much appreciated.

Answer 1

You can filter Collection, like this:
$next = $item->id + 1;
$catalogue->filter(function($item) use ($next ) {
return $item->id == $next;
})->first();
I use global method added to Collection class:
/**
* Returns first object from collection which meets attribute criteria
*
* #param string $attributeName name of attribute we are looking for
* #param string $attributeValue value of attribute that have to be met
* #return \Illuminate\Database\Eloquent\Collection
*/
public function findByAttribute($attributeName, $attributeValue)
{
return $this->filter(function($item) use ($attributeName, $attributeValue) {
return $item->{$attributeName} == $attributeValue;
})->first();
}
In this case I would use this method this way:
$catalogue->items->findByAttribute('id', $next);
In both examples I assume You have $item object to reffer to.

Answer 2

You can use Pagination
Catalogue::first()->items()->paginate(1);

Answer 3

Actually, it was much simpler. This did the trick:
$nextProdId = $this->items()->where('product_id', '>', $product->id)->min('product_id');
return Product::find($nextProdId);
I had to add () after 'items' to enable 'where' clause and make it searchable basically.