How to use hasOne relationship in Laravel?

Laravel, one of the most popular PHP frameworks, has several functions, like user online or offline on Laravel,  that make it attractive for developers, one of them being hasOne, which basically allows communication or relationship between two tables. Its name means "create a one-to-one relationship".

Before explaining how to use this useful Laravel relation, let's define what this framework consists of and what it can achieve. Among the benefits that Laravel offers to develop applications in PHP, the ease of development stands out, since it integrates BackEnd tools. We have the best Laravel developers here. Let's talk!

Also, combining the best packages in the PHP ecosystem, it offers as a result a robust and friendly framework for developers. It has the ability to create dynamic sites with an innovative template engine, as well as offering the developer a very secure and bulletproof migration process.

Laravel comes with pre-installed target-oriented libraries and uses a PHP unit to automate code testing when developing web applications.

Using the hasOne relationship in Laravel

First of all, we can explain a simple example of the use of hasOne: if an article has comments and we want to take one of them with the details of the article, we can use the hasOne relationship or a user can have a profile table.

It should be noted that Laravel relationships do not create connections in the database, these relationships are created in the application layer and this produces the final result. The hasOne relation accepts three parameters: model name, foreign_key, and the third, optional, is local_key.

This is the syntax:

<?php
 
namespace App\Models;
 
use Illuminate\Database\Eloquent\Model;
 
class Owner extends Model
{
     
    public function child()
    {
        return $this->hasOne(child::class,'foreign_key','local_key');
    }
}

In the above syntax, we have used the belongsTo method with 3 parameters, so here Child::class is the name of the model we want to relate to, Foreign_key means the column name of the child table, and local_key means the column name of your own table.

Laravel itself is not capable of creating an inner join query, so it does it separately and then joins the data, using it as follows:

Article::with('child')->get();

This command line will allow you to get back all the articles next to the first comment.

Let's explain the use of hasOne in an article comment tables

1. Create a comment and article model

Item Model:

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Article extends Model
{
    use HasFactory;
}

Comment model:

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Comment extends Model
{
    use HasFactory;
}

2. Create the hasOne relationship in the item model

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Article extends Model
{
    use HasFactory;

    public function comment(){
        return $this->hasOne(Comment::class);
    }
}

In the code, a method comment was created and hasOne was used for the relationship to the comment model. When doing this, Laravel assumes that the table name is comment and the foreign key is the article_id table.

How to build a live comment system with Laravel and Vue.js? Read more in our blog.

3. Use relation in controller

Let's create a controller and import the necessary classes to access the model and its relationships:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Models\Article;

class ArticleController extends Controller
{

    public function index(Request $request)
    {

        $article=Article::with("comment")->first();
        dump($article);

        dump($article->comment);

    }
}

4. Create the route

Lastly, create the route in web.php

Route::get('/articles',[ArticleController::class, 'index']);

This is an example of how to use the hasOne relationship in a Laravel Project, ideal for making the developer's job faster and easier, being able to create a communication bridge or relationship between two data tables.

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