Laravel custom relationship

App\Eloquent\Concerns\HasCustomRelationships.php

<?php

namespace App\Eloquent\Concerns;

use Illuminate\Support\Str;
use App\Eloquent\Relationships\LeaveableMorphToMany;

/**
 * Trait HasCustomRelationships
 *
 * @mixin \Eloquent
 */
trait HasCustomRelationships
{
  /**
   * Define a polymorphic, inverse many-to-many relationship (leaveable).
   *
   * @param string $related
   * @param string $name
   * @param string $table
   * @param string $foreignPivotKey
   * @param string $relatedPivotKey
   * @param string $parentKey
   * @param string $relatedKey
   *
   * @return \App\Eloquent\Relationships\LeaveableMorphToMany
   */
  public function leaveableMorphedByMany($related, $name, $table = null, $foreignPivotKey = null,
                                         $relatedPivotKey = null, $parentKey = null, $relatedKey = null)
  {
    $foreignPivotKey = $foreignPivotKey ?: $this->getForeignKey();

    // For the inverse of the polymorphic many-to-many relations, we will change
    // the way we determine the foreign and other keys, as it is the opposite
    // of the morph-to-many method since we're figuring out these inverses.
    $relatedPivotKey = $relatedPivotKey ?: $name . '_id';

    return $this->leaveableMorphToMany(
      $related, $name, $table, $foreignPivotKey,
      $relatedPivotKey, $parentKey, $relatedKey, true
    );
  }

  /**
   * Define a polymorphic many-to-many relationship (leaveable).
   *
   * @param string $related
   * @param string $name
   * @param string $table
   * @param string $foreignPivotKey
   * @param string $relatedPivotKey
   * @param string $parentKey
   * @param string $relatedKey
   * @param bool   $inverse
   *
   * @return \App\Eloquent\Relationships\LeaveableMorphToMany
   */
  public function leaveableMorphToMany($related, $name, $table = null, $foreignPivotKey = null,
                              $relatedPivotKey = null, $parentKey = null,
                              $relatedKey = null, $inverse = false)
  {
    $caller = $this->guessBelongsToManyRelation();

    // First, we will need to determine the foreign key and "other key" for the
    // relationship. Once we have determined the keys we will make the query
    // instances, as well as the relationship instances we need for these.
    $instance = $this->newRelatedInstance($related);

    $foreignPivotKey = $foreignPivotKey ?: $name . '_id';

    $relatedPivotKey = $relatedPivotKey ?: $instance->getForeignKey();

    // Now we're ready to create a new query builder for this related model and
    // the relationship instances for this relation. This relations will set
    // appropriate query constraints then entirely manages the hydrations.
    if (!$table) {
      $words = preg_split('/(_)/u', $name, -1, PREG_SPLIT_DELIM_CAPTURE);

      $lastWord = array_pop($words);

      $table = implode('', $words) . Str::plural($lastWord);
    }

    return new LeaveableMorphToMany($instance->newQuery(), $this, $name, $table,
      $foreignPivotKey, $relatedPivotKey, $parentKey ?: $this->getKeyName(),
      $relatedKey ?: $instance->getKeyName(), $caller, $inverse);
  }
}

App\Eloquent\Relationships\LeaveableMorphToMany.php

<?php

namespace App\Eloquent\Relationships;

use Illuminate\Database\Eloquent\Relations\MorphToMany;

class LeaveableMorphToMany extends MorphToMany
{

}

App\Models\Stable.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use App\Eloquent\Concerns\HasCustomRelationships;

class Stable extends Model
{
  use HasCustomRelationships;

  public function wrestlers()
  {
    return $this->leaveableMorphedByMany(Wrestler::class, 'member')->withPivot('left_at');
  }
}

App\Models\Wrestler.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use App\Eloquent\Concerns\HasCustomRelationships;

class Wrestler extends Model
{
  use HasCustomRelationships;

  public function stables()
  {
    return $this->leaveableMorphToMany(Stable::class, 'member');
  }
}