Eloquent Inheritance

Single table inheritance is a way to emulate object-oriented inheritance in a relational database. While other frameworks like Ruby on Rails have a built-in implementation for this pattern, Laravel has not. This package aims to provide an as easy as possible implementation for Laravel.

Installation

You can install the package via composer:

composer require proai/eloquent-inheritance

Please note that you need at least PHP 8.0 and Laravel 9 for this package.

Usage

First you need to add the Inheritance trait to your root model:

use ProAI\Inheritance\Inheritance;

class Pet extends Model
{
    use Inheritance;

    //
}

Then you can extend the root model by other models that use the same table:

class Cat extends Pet
{
    //
}

class Dog extends Pet
{
    //
}

Note that you need a table pets with a column called type in order to make the example above work.

Whenever a Cat or Dog model is instantiated, the attribute type will be set to the classname of the class (e.g. App\Models\Cat).

Other than that there is no magic and a Cat or a Dog model will behave just like a normal Eloquent model. You can define cat or dog specific attributes and relationships on these models. An attribute only set for dogs for example should be a nullable column on the table, so that it is set for dogs but null for other pets.

Root model behaviour

You can query the root model like any other model. However, the returned models will be transformed based by the type name. For example if there is one cat and one dog in the database, Pet::all(); will return one Dog and one Cat model.

It is not possible to use new Pet($attributes); when you specify the type in $attributes. Please use the static method Pet::new($attributes) instead. This method returns a new model based on the given type. For example if the type in $attributes is App\Models\Cat, it will return an instance of App\Models\Cat. If no type is specified, an instance of App\Models\Pet will be returned.

Custom type names

If you want to use different names for the type column than the classname, you can use the static $inheritanceMap property:

class Pet extends Model
{
    use Inheritance;

    protected static $inheritanceMap = [
        'cat' => Cat::class,
        'dog' => Dog::class,
    ];
}

Custom type column

By default the name of the type column is type. However, you can set a custom type column name:

use ProAI\Inheritance\Inheritance;

class Pet extends Model
{
    use Inheritance;

    protected static $inheritanceColumn = 'pet_type';
}

Support

Bugs and feature requests are tracked on GitHub.

License

This package is released under the MIT License.