Laravel alternative to paginate on collection? - laravel

Question

On my website, I have Submissions, and submissions can have comments.
Comments can have upvotes and downvotes, leading to a total "score" for the comment.
In this example, before passing the comments to the view, I sort them by score.
$comments = Comment::where('submission_id', $submission->id)->where('parent_id', NULL)->get();
$comments = $comments->sortByDesc(function($comment){
return count($comment['upvotes']) - count($comment['downvotes']);
});
This works fine. The higher the score of a comment, the higher it is sorted.
However, I want to paginate these results.
If I do ->paginate(10) instead get(), the following sortByDesc will only sort those 10 results.
So logically I would want to add the paginator after the sortByDesc like so:
$comments = $comments->sortByDesc(function($comment){
return count($comment['upvotes']) - count($comment['downvotes']);
})->paginate(10);
However this will return the error:
Method Illuminate\Database\Eloquent\Collection::paginate does not
exist.
as expected.
My question is, what is the alternative to using paginate in this situation?
EDIT:
When trying the response of #party-ring (and switching the double quotes and single quotes) I get the following error:
SQLSTATE[42000]: Syntax error or access violation: 1064 You have an
error in your SQL syntax; check the manual that corresponds to your
MariaDB server version for the right syntax to use near '["upvotes"])
- count($comment["downvotes"]) desc limit 10 offset 0' at line 1 (SQL: select * from comments where submission_id = 1 and parent_id is
null order by count($comment["upvotes"]) -
count($comment["downvotes"]) desc limit 10 offset 0)

Answer 1

You are trying to paginate after the get, the solution i try on my website is this and it works
$users = User::where('votes', '>', 100)->get();
$page = Input::get('page', 1); // Get the ?page=1 from the url
$perPage = 15; // Number of items per page
$offset = ($page * $perPage) - $perPage;
return new LengthAwarePaginator(
array_slice($users->toArray(), $offset, $perPage, true), // Only grab the items we need
count($users), // Total items
$perPage, // Items per page
$page, // Current page
['path' => $request->url(), 'query' => $request->query()] // We need this so we can keep all old query parameters from the url
);

Answer 2

You could add a macro:
if (!Collection::hasMacro('paginate')) {
Collection::macro('paginate', function ($perPage = 25, $page = null, $options = []) {
$options['path'] = $options['path'] ?? request()->path();
$page = $page ?: (Paginator::resolveCurrentPage() ?: 1);
return new LengthAwarePaginator(
$this->forPage($page, $perPage)->values(),
$this->count(),
$perPage,
$page,
$options
);
});
}
Then you can use a collection to paginate your items:
collect([1,2,3,4,5,6,7,8,9,10])->paginate(5);
See Extending Collections under Introduction

Answer 3

Give this a try:
$comments = Comment::where('submission_id', $submission->id)
->where('parent_id', NULL)
->orderBy(DB::raw("count($comment['upvotes']) - count($comment['downvotes'])"), 'desc')
->paginate(10);`
SortBy returns a Collection, whereas you can only call paginate on an instance of QueryBuilder. OrderBy should return an instance of QueryBuilder, and you should be able to do the subtraction using a DB::raw statement.
** edit
I have just read about orderByRaw, which might be useful in this scenario:
$comments = Comment::where('submission_id', $submission->id)
->where('parent_id', NULL)
->orderByRaw('(upvotes - downvotes) desc')
->paginate(10);`
You might have to play around a bit with your subtraction above as I don't know the structure of your comments table.
A couple of links which might be useful:
laravel orderByRaw() on the query builder
https://laraveldaily.com/know-orderbyraw-eloquent/