How to define a one-to-one relationship in Eloquent?
In Laravel Eloquent, defining a one-to-one relationship requires first setting the database foreign key and associating the model using hasOne and belongsTo methods. 1. Create a unique foreign key in the phones table through foreignId('user_id')->unique(); 2. Define public function phone() { return $this->hasOne(Phone::class); } means that the user has a phone; 3. Define public function user() { return $this->belongsTo(User::class); } means that the phone belongs to a user; 4. You can access the associated data through $user->phone->number, or use $user->phone()->create() to create a record; 5. If the foreign key name is not the default user_id, you can specify a custom field name in the second parameter. After correct configuration, Eloquent will automatically handle the associated operations to fully realize one-to-one relationship.
In Laravel's Eloquent ORM, defining a one-to-one relationship is straightforward and follows a simple tradition. This type of relationship exists when one record in a database table is associated with exactly one record in another table.
1. Database Setup
First, ensure your database schema supports the one-to-one relationship. For example, let's say a User has one Phone . You'd set up your tables like this:
// In a migration for 'users' table
Schema::create('users', function (Blueprint $table) {
$table->id();
$table->string('name');
$table->timestamps();
});
// In a migration for 'phones' table
Schema::create('phones', function (Blueprint $table) {
$table->id();
$table->foreignId('user_id')->unique(); // user_id is foreign key and unique
$table->string('number');
$table->timestamps();
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
});? The
user_idin thephonestable must beuniqueto enforce one-to-one mapping.
2. Define the Relationship in Eloquent Models
Now, define the relationship in your models.
In the User model:
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class User extends Model
{
public function phone()
{
return $this->hasOne(Phone::class);
}
}✅
hasOne()means "a user has one phone".
In the Phone model:
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class Phone extends Model
{
public function user()
{
return $this->belongsTo(User::class);
}
}✅
belongsTo()means "a phone belongs to a user".
3. Usage Examples
Once defined, you can use the relationship like this:
// Get a user's phone
$user = User::find(1);
echo $user->phone->number;
// Get the user from a phone
$phone = Phone::find(1);
echo $phone->user->name;
// Create a phone for a user
$user = User::find(1);
$user->phone()->create([
'number' => '555-1234'
]);? Eloquent automatically uses the model name and
_idsuffix (eg,user_id) as the foreign key unless you specify otherwise.
Optional: Custom Foreign Key
If your foreign key is not user_id , you can specify it:
return $this->hasOne(Phone::class, 'custom_user_id');
Or in belongsTo :
return $this->belongsTo(User::class, 'custom_user_id');
That's it. One-to-one relations in Eloquent are clean and intuitive—just use hasOne on the "owner" side and belongsTo on the "dependent" side. Basically just set up the right migration and model methods, and Eloquent handles the rest.
The above is the detailed content of How to define a one-to-one relationship in Eloquent?. For more information, please follow other related articles on the PHP Chinese website!
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