Mastering Advanced Eloquent Relationships

Polymorphic Relationships

Imagine you have posts, videos, and events, and users can comment on all of them. Instead of creating post_comments, video_comments, etc., use a Polymorphic One-to-Many relationship.

// Comment Model
public function commentable()
{
    return $this->morphTo();
}
 
// Post Model
public function comments()
{
    return $this->morphMany(Comment::class, 'commentable');
}

This allows a single comments table to link to any other model.

Many-to-Many with Custom Pivots

Sometimes the link between two models has data of its own. For example, a User belongs to a Role, but the relationship has an expires_at date.

Define a custom Pivot model:

use Illuminate\Database\Eloquent\Relations\Pivot;
 
class RoleUser extends Pivot
{
    protected $casts = [
        'expires_at' => 'datetime',
    ];
}

Then specify it in your relationship:

public function roles()
{
    return $this->belongsToMany(Role::class)
                ->using(RoleUser::class)
                ->withPivot('expires_at');
}

Conclusion

Eloquent is capable of handling virtually any data structure you throw at it. Mastering these relationships keeps your database clean and your code expressive.