How To Define Dynamic Relationships With Laravel Framework

Eloquent relationships are defined as methods on your Eloquent model classes. Since, like Eloquent models themselves, relationships also serve as powerful query builders, defining relationships as methods provides powerful method chaining and querying capabilities. Use subqueries to create dynamic relationships in Laravel.

Dynamic Relationships 

if we want to define a “one-to-one” relationship between Post and User model where the Post belongs to the User, you can define it like so.

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<?php
namespace App;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{

    public function user()
    {
        return $this->belongsTo('App\User');
    }
}

Here, the Eloquent will try to match the user_id from the Post model to an id on the User model and based on that will fetch the records.

This is one way to define relationships. But there’s another way in Eloquent using which you can define relationships on-the-fly outside of the models. Enter resolveRelationUsing method.

resolveRelationUsing method which can be used to define relations between Eloquent models outside of model like so.

You may use the resolveRelationUsing method to define relations between Eloquent models at runtime. While not typically recommended for normal application development, this may occasionally be useful when developing Laravel packages:

use App\Post;
use App\User;

Post::resolveRelationUsing('User', function ($postModel) {
    return $postModel->belongsTo(Customer::class, 'user_id');
});

When defining dynamic relationships, always provide explicit key name arguments to the Eloquent relationship methods.