php Laravel中的多对多关系来自一系列ID Raw

Posted 2021-05-05

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Relations\BelongsToMany;

use Illuminate\Support\Arr;
use Illuminate\Support\Str;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Collection;
use Illuminate\Database\Eloquent\ModelNotFoundException;

class BelongsToManyFromColumn extends BelongsToMany
{
	
    public function __construct(Builder $query, Model $parent, $foreignKey, $relatedKey, $relationName = null)
    {
        parent::__construct($query, $parent, 'mybb_usergroups', $foreignKey, $relatedKey, $relationName);
    }
	
    public function addEagerConstraints(array $models)
    {
		/*
			ORIGINAL:
			$this->query->whereIn($this->getQualifiedForeignKeyName(), $this->getKeys($models));
			
			We replace this with the code below, because we already have the IDs from our models as opposed to doing an inner join.
		*/
		
		$key = (string)$this->relatedKey;
		$keys = collect($models)->pluck($key)->flatten()->unique()->all();
		
        $this->query->whereIn($this->getQualifiedForeignKeyName(), $keys);
    }
	
    public function addConstraints()
    {
		/*
			ORIGINAL:
			$this->performJoin();

			if (static::$constraints) {
				$this->addWhereConstraints();
			}
			
			We remove the performJoin() method because we already have the IDs from our model.
		*/
        if (static::$constraints) {
            $this->addWhereConstraints();
        }
    }
	
    protected function aliasedPivotColumns()
    {
		/*
			ORIGINAL:
			$defaults = [$this->foreignKey, $this->relatedKey];

			return collect(array_merge($defaults, $this->pivotColumns))->map(function ($column) {
				return $this->table.'.'.$column.' as pivot_'.$column;
			})->unique()->all();
			
			We use the foreignKey as the relatedKey because we don't really have a relatedKey(gids) on the table structure for our mybb_users group since we already have the IDs from the models
		*/
		return [
			$this->table.'.'.$this->foreignKey.' as pivot_'.$this->foreignKey,
			$this->table.'.'.$this->foreignKey.' as pivot_'.$this->relatedKey,
		];
    }
	
    public function match(array $models, Collection $results, $relation)
    {
		/*
			There is quite a bit of modification here, you'll just have to read up the source and understand it but basically
			we get the list of groups from the buildDictionary function and then we go through the Eloquent models for the User model
			and attach any that are in the relatedKey(gids) array.
		*/
        $dictionary = $this->buildDictionary($results);
		
        foreach ($models as $model) {
			$collections = [];
			foreach($model->{$this->relatedKey} as $key) {
				if (isset($dictionary[$key])) {
					$collections[] = $dictionary[$key];
				}
			}
			$model->setRelation(
				$relation, $this->related->newCollection($collections)
			);
        }

        return $models;
    }
	
    protected function buildDictionary(Collection $results)
    {
		/*
			This justs creates an array and keys it by its ID (gid)
		*/
        $dictionary = [];

        foreach ($results as $result) {
            $dictionary[$result->pivot->{$this->foreignKey}] = $result;
        }
		
        return $dictionary;
    }
}