View file vendor/illuminate/database/Concerns/BuildsQueries.php

<?php

namespace Illuminate\Database\Concerns;

use Illuminate\Container\Container;
use Illuminate\Pagination\Paginator;
use Illuminate\Pagination\LengthAwarePaginator;

trait BuildsQueries
{
    /**
     * Chunk the results of the query.
     *
     * @param  int  $count
     * @param  callable  $callback
     * @return bool
     */
    public function chunk($count, callable $callback)
    {
        $this->enforceOrderBy();

        $page = 1;

        do {
            // We'll execute the query for the given page and get the results. If there are
            // no results we can just break and return from here. When there are results
            // we will call the callback with the current chunk of these results here.
            $results = $this->forPage($page, $count)->get();

            $countResults = $results->count();

            if ($countResults == 0) {
                break;
            }

            // On each chunk result set, we will pass them to the callback and then let the
            // developer take care of everything within the callback, which allows us to
            // keep the memory low for spinning through large result sets for working.
            if ($callback($results, $page) === false) {
                return false;
            }

            unset($results);

            $page++;
        } while ($countResults == $count);

        return true;
    }

    /**
     * Execute a callback over each item while chunking.
     *
     * @param  callable  $callback
     * @param  int  $count
     * @return bool
     */
    public function each(callable $callback, $count = 1000)
    {
        return $this->chunk($count, function ($results) use ($callback) {
            foreach ($results as $key => $value) {
                if ($callback($value, $key) === false) {
                    return false;
                }
            }
        });
    }

    /**
     * Execute the query and get the first result.
     *
     * @param  array  $columns
     * @return \Illuminate\Database\Eloquent\Model|object|static|null
     */
    public function first($columns = ['*'])
    {
        return $this->take(1)->get($columns)->first();
    }

    /**
     * Apply the callback's query changes if the given "value" is true.
     *
     * @param  mixed  $value
     * @param  callable  $callback
     * @param  callable  $default
     * @return mixed|$this
     */
    public function when($value, $callback, $default = null)
    {
        if ($value) {
            return $callback($this, $value) ?: $this;
        } elseif ($default) {
            return $default($this, $value) ?: $this;
        }

        return $this;
    }

    /**
     * Pass the query to a given callback.
     *
     * @param  \Closure  $callback
     * @return \Illuminate\Database\Query\Builder
     */
    public function tap($callback)
    {
        return $this->when(true, $callback);
    }

    /**
     * Apply the callback's query changes if the given "value" is false.
     *
     * @param  mixed  $value
     * @param  callable  $callback
     * @param  callable  $default
     * @return mixed|$this
     */
    public function unless($value, $callback, $default = null)
    {
        if (! $value) {
            return $callback($this, $value) ?: $this;
        } elseif ($default) {
            return $default($this, $value) ?: $this;
        }

        return $this;
    }

    /**
     * Create a new length-aware paginator instance.
     *
     * @param  \Illuminate\Support\Collection  $items
     * @param  int  $total
     * @param  int  $perPage
     * @param  int  $currentPage
     * @param  array  $options
     * @return \Illuminate\Pagination\LengthAwarePaginator
     */
    protected function paginator($items, $total, $perPage, $currentPage, $options)
    {
        return Container::getInstance()->makeWith(LengthAwarePaginator::class, compact(
            'items', 'total', 'perPage', 'currentPage', 'options'
        ));
    }

    /**
     * Create a new simple paginator instance.
     *
     * @param  \Illuminate\Support\Collection  $items
     * @param  int $perPage
     * @param  int $currentPage
     * @param  array  $options
     * @return \Illuminate\Pagination\Paginator
     */
    protected function simplePaginator($items, $perPage, $currentPage, $options)
    {
        return Container::getInstance()->makeWith(Paginator::class, compact(
            'items', 'perPage', 'currentPage', 'options'
        ));
    }
}