Laravel - Convert array back to a collection

Question

I am trying to get a collection of categories only if they are in the products table. My categories table has 300 items. I only want a collection if a category is attached in the products table. The $categories collection should only result in about 10 categories because there are only about 10 products that have different category_ids

$products = DB::table('products')->groupBy('category_id')->get();

foreach($products as $product){
        $categories[] = DB::table('categories')->where('id', '=', $product->category_id)->first();
}

$categories = collect($categories)->all();

Maybe I am going about this wrong and should use a different query builder method?

The end result $categories does get the results I am after but in my blade I get the "Trying to get property of non-object" error.

Please see my edit. This can be done with 3 lines of the query builder. — N Mahurin
– N Mahurin, Commented May 24, 2019 at 16:39

thisiskelvin · Accepted Answer · 2019-05-24 15:57:27Z

6

If using $categories in your blade file as a collection, you will need to remove the ->all() method.

->all() is converting the collection into an array after it is being created:

$categories = collect($categories);

answered May 24, 2019 at 15:57

thisiskelvin

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1 Comment

dustbuster Over a year ago

Yup, it's that simple. I needed countable back!

Davit Zeynalyan · Accepted Answer · 2019-05-24 16:32:53Z

2

You get Trying to get property of non-object because one of

DB::table('categories')->where('id', '=', $product->category_id)->first();

return null value.
You can fix it this way

$products = DB::table('products')->groupBy('category_id')->get();

$categories = collect();
foreach($products as $product){
    $category = DB::table('categories')->where('id', '=', $product->category_id)->first();
    if ($category) {
        $categories->push($category); 
    }
}

If you want to get collection instance you must be use collect() helper method with array argument. For example

collect($categories); // is_array(categories) is true

You are doing many request in foreach. That is not right way. Instead it you can achieve collection instance doing only 2 request.

 $categoryIds = DB::table('products')->pluck('category_id')->toArray();
 $categories = DB::table('categories')->whereIn('id', $categoryIds)->get();

See docs https://laravel.com/docs/5.8/queries#retrieving-results

edited May 24, 2019 at 16:32

answered May 24, 2019 at 15:52

Davit Zeynalyan

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3 Comments

AbraCadaver Over a year ago

Code dump, no text no explanation? With 4K rep I'd think you would know to add something.

Davit Zeynalyan Over a year ago

@AbraCadaver Edit answer with explanation. If you want you can improve it. but this is solution with 2 quesries

Chad Priddle Over a year ago

This did the trick. Thanks. I would agree however that doing it through a relationship would be a better use of code

N Mahurin · Accepted Answer · 2019-05-24 17:01:43Z

1

This can be done with one simple eloquent query. There's no need to use query builder unless you're doing something overly complex (in my opinion).

whereHas() will only return Categories that have Products.

Categories::with('products')->whereHas('products')->get();

As long as the relationships are correct on the models the above is what you're looking for. As pointed out in the comments, you need models and relationships. Laravel uses the MVC pattern, and the first letter stands for model so I'm going to guess you're using them. If not let me know and I can help set those up because you should be using them.

And if you NEED to use the query builder clean that code up and use something like this so you don't have to worry about recollecting. Also check out the hydrate() method to change these generic class instances into instances of the Categories model.

DB::table('categories')->whereIn('id', function($q){
    $q->select('category_id')->from('products');
})->get();

edited May 24, 2019 at 17:01

answered May 24, 2019 at 16:03

N Mahurin

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1 Comment

thisiskelvin Over a year ago

This may require the creation of the relationships and models so would be good to explain in your answer.

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