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Osm Admin: Subclasses

2021 November Osm Admin

6 months ago ∙ 1 minute read

As described in Migrations, most data objects of the same class will be stored in a database table.

But what about subclasses? In an e-commerce application, bags, dresses, and digital products, collectively known as subclasses, are all products stored in products table, and they may have bad-specific, dress-specific or digital product specific properties that should also be stored there.

This article describes how subclasses are defined and stored in Osm Admin.

type Property

In the base class, Product, add type property using Type trait:

use Osm\Core\Traits\SubTypes;
...

/**
 * @property string $sku #[Serialized]
 * @property string $description #[Serialized]
 */
#[Storage\Table('products')]
class Product extends Object_
{
    use Id, SubTypes;
}

In child classes, assign the type property using #[Type] attribute:

/**
 * @property string $color #[Serialized]
 */
#[Type('bag')]
class Bag extends Product {
}  

/**
 * @property string $color #[Serialized]
 * @property string $size #[Serialized]
 */
#[Type('dress')]
class Dress extends Product {
}  

/**
 * @property string $file #[Serialized]
 */
#[Type('digital')]
class Digital extends Product {
}  

When the type property is serialized into a table record, it's computed from the #[Type] attribute. This way Osm Admin known what class to instantiate when loading data back from the database.

Type-Specific Properties

In the above code sample, color, size and file are examples of type-specific properties. These properties are stored in the database table in the same way the Product class properties are stored: in the data JSON column, or, in case a Column\* attribute is specified, in a dedicated column.

In case you use the same property in several subclasses, make sure it has the same definition. For example, the color property is defined in both Bag and Dress class, and it has exactly the same definition.