`$has_one` (one-to-one)¶

The $has_one relationship in ActiveRecord represents a one-to-one association between two database tables. It allows you to specify that a record in one table is associated with exactly one record in another table. To define a $has_one relationship, you need to configure the following properties:

Name of the Relationship: This property specifies the name of the relationship, which is used to access the associated record. It is typically set as a string representing the name of the associated model.
```
static $has_one = ['profile' => []];
```
Class Name (Optional): This property allows you to explicitly specify the class name of the associated model if it differs from the relationship name. This can be useful if your relationship and model names do not follow the default naming conventions.
```
static $has_one = [
    'customProfile' => [
        'class_name' => 'Profile'
    ]
];
```
Foreign Key (Optional): By default, ActiveRecord assumes that the foreign key in the associated table is derived from the name of the current model and suffixed with "_id" (e.g., "user_id" for a User model). You can specify a different foreign key if needed. This property is optional.
```
static $has_one = [
    'customProfile' => [
        'class_name' => 'Profile', 
        'foreign_key' => 'custom_user_id'
    ]
];
```
Primary Key (Optional): This property allows you to specify the primary key of the associated table if it is different from the default "id" column. Use this when your associated table uses a different primary key column. This property is optional.
```
static $has_one = [
    'profile' => [
        'primary_key' => 'profile_id'
    ]
];
```
Order (Optional): You can specify the order in which the associated records should be retrieved using the order property. This property is optional.
```
static $has_one = [
    'profile' => [
        'order' => 'created_at DESC'
    ]
];
```
Conditions (Optional): You can specify conditions for retrieving the associated record using the conditions property. This property allows you to filter the associated record based on specific criteria. This property is optional.
```
static $has_one = [
    'profile' => [
        'conditions' => [
            'active' => true
        ]
    ]
];
```

Example of Usage:

class User extends ActiveRecord\Model {
    static $has_one = [
        'profile' => []
    ];
}

class Profile extends ActiveRecord\Model {
    static $belongs_to = [
        'user' => []
    ];
}

In this example, a User model has a $has_one relationship with the Profile model. It allows you to access a user's profile information through the profile property.

The $has_one relationship simplifies working with one-to-one associations in your database, making it easy to retrieve and manipulate associated records.

$has_one (one-to-one)¶

`$has_one` (one-to-one)¶