Laravel custom morph relationship - php

Question

I'd like to use Laravel Eloquent Polymorphic Relationships however it doesn't seem to be setup to work with my table structure.
Essentially I have a gamedata table which includes all the different types of gamedata (nation, league, team, player etc). For each type I have multiple tables with information separated by game_id. So there would be one row for the nation "England" in the gamedata table, which has 7 corresponding rows in the nations table with data from 7 different game_ids.
I'd like to be able to select some rows from the gamedata table and their corresponding rows from the appropriate table depending on it's type.
This is easy enough to do on a one to one relationship, but seems impossible to do with a one to many relationship.
Here is the gamedata table.
CREATE TABLE `gamedata` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`data_type` varchar(16) COLLATE utf8mb4_unicode_ci NOT NULL,
`name` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `data_id` (`data_id`,`type`),
FULLTEXT KEY `name` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
And then lots of tables like this (lots of columns removed for ease of reading):
CREATE TABLE `nations` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`game_id` tinyint(3) unsigned NOT NULL,
`gamedata_id` int(10) unsigned NOT NULL,
`name` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
`short_name` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
/* more specific columns removed for ease of reading */
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
CREATE TABLE `leagues` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`game_id` tinyint(3) unsigned NOT NULL,
`gamedata_id` int(10) unsigned NOT NULL,
`name` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
`short_name` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
/* more specific columns removed for ease of reading */
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
CREATE TABLE `teams` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`game_id` tinyint(3) unsigned NOT NULL,
`gamedata_id` int(10) unsigned NOT NULL,
`name` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
`short_name` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
/* more specific columns removed for ease of reading */
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
So some rows on the gamedata table might look like this:
(144, 'nation', 'Some Nation'),
(145, 'nation', 'Another Nation'),
(146, 'league', 'Some League'),
(147, 'league', 'Another League'),
(148, 'team', 'Some Team'),
(149, 'team', 'Another Team');
So I should be able to do a polymorphic relationship from the "data_type" column and the "data_id" column to get the corresponding row from the appropriate table.
But none of the built in relationships (morphTo, morphMany, morphedByMany) etc seem to be able to handle it.
It seems like what I want is the morphTo() relationship but it seems to restrict itself to only returning one related model. All the relationships that accept multiple models require a specific model to be defined.
// This would work fine if I only wanted one related model. "data_type" being the class and "id" corresponding to "gamedata_id" on relevent table.
$this->morphTo('data');
// These require me to be explicit about the class instantiating rather than using from the "data_type" column
$this->morphMany(???, 'data');
$this->morphToMany(???, 'data');
$this->morphedByMany(???, 'data');
Is there a way to do this using the existing Laravel Relationships? Or is there a simple way to create my own relationship class based on morphTo that would suit my needs?

Answer 1

I think i've come up with a custom solution by extending the morphTo class.
namespace App;
use Illuminate\Database\Eloquent\Collection;
use Illuminate\Database\Eloquent\Relations\MorphTo;
/**
* #mixin \Illuminate\Database\Eloquent\Builder
*/
class MorphHasMany extends MorphTo
{
/**
* Get the results of the relationship.
*
* #return mixed
*/
public function getResults()
{
return $this->ownerKey ? $this->query->get() : null;
}
/**
* Match the results for a given type to their parents.
*
* #param string $type
* #param \Illuminate\Database\Eloquent\Collection $results
* #return void
*/
protected function matchToMorphParents($type, Collection $results)
{
$ownerKeyName = $this->ownerKey ?: $results->first()->getKeyName();
foreach ($results->groupBy($ownerKeyName) as $ownerKey => $result) {
if (isset($this->dictionary[$type][$ownerKey])) {
foreach ($this->dictionary[$type][$ownerKey] as $model) {
$model->setRelation($this->relation, $result);
}
}
}
}
}
The morphTo() class already returns a Collection of results, but either uses first() or multiple instances of setRelation() to mean there is only one set. By overloading getResults() and matchToMorphParents() I can modify this behaviour to allow setting of a Collection instead.
In order to define the relationship i'll need a custom morphHasMany() method. This could be added to a base Model.php that extends Eloquent\Model.
/**
* Define a polymorphic has many relationship.
*
* #param string $name
* #param string $type
* #param string $id
* #param string $ownerKey
* #return MorphHasMany
*/
public function morphHasMany($name = null, $type = null, $id = null, $ownerKey = null)
{
// If no name is provided, we will use the backtrace to get the function name
// since that is most likely the name of the polymorphic interface. We can
// use that to get both the class and foreign key that will be utilized.
$name = $name ?: $this->guessBelongsToRelation();
list($type, $id) = $this->getMorphs(
Str::snake($name), $type, $id
);
// If the type value is null it is probably safe to assume we're eager loading
// the relationship. In this case we'll just pass in a dummy query where we
// need to remove any eager loads that may already be defined on a model.
if (empty($class = $this->{$type})) {
return new MorphHasMany($this->newQuery()->setEagerLoads([]), $this, $id, $ownerKey, $type, $name);
} else {
$instance = $this->newRelatedInstance(
static::getActualClassNameForMorph($class)
);
return new MorphHasMany($instance->newQuery(), $this, $id, $ownerKey ?? $instance->getKeyName(), $type, $name);
}
}
Then simply define it just like the usual morphTo() method.
public function data()
{
return $this->morphHasMany();
}
Or in my case:
public function data()
{
return $this->morphHasMany('data', 'data_type', 'id', 'gamedata_id');
}
So far no problems, but of course I may run into some in the future.