Posts published in “Abstract Factory”

Abstract Factory is a creational design pattern that lets you produce families of related objects without specifying their concrete classes.

Benefit:

• You can be sure that the products you’re getting from a factory are compatible with each other.
• You avoid tight coupling between concrete products and client code.
• Single Responsibility Principle. You can extract the product creation code into one place, making the code easier to support.
• Open/Closed Principle. You can introduce new variants of products without breaking existing client code.

Disadvantage:

• The code may become more complicated since you need to introduce a lot of new subclasses to implement the pattern. The best case scenario is when you’re introducing the pattern into an existing hierarchy of creator classes.

Why?

For example. Our online furniture store has several variants of this family.

Products Chair + Sofa + Bed are available in these variants: Modern, Classic, Wooden.

A customer wants to order a Modern-style sofa. You need a way to create individual furniture objects so that they match other objects of the same family. You don’t want to change existing code when adding new products or families of products to the program. Furniture vendors update their catalogs very often, and you wouldn’t want to change the core code each time it happens.

Sample Code:

<?php

namespace JSTechRoad\AbstractFactory\Conceptual;

interface AbstractFactory
{
    public function createProductA(): AbstractProductA;

    public function createProductB(): AbstractProductB;
}

class ConcreteFactory1 implements AbstractFactory
{
    public function createProductA(): AbstractProductA
    {
        return new ConcreteProductA1();
    }

    public function createProductB(): AbstractProductB
    {
        return new ConcreteProductB1();
    }
}

class ConcreteFactory2 implements AbstractFactory
{
    public function createProductA(): AbstractProductA
    {
        return new ConcreteProductA2();
    }

    public function createProductB(): AbstractProductB
    {
        return new ConcreteProductB2();
    }
}

interface AbstractProductA
{
    public function usefulFunctionA(): string;
}

class ConcreteProductA1 implements AbstractProductA
{
    public function usefulFunctionA(): string
    {
        return "The result of the product A1.";
    }
}

class ConcreteProductA2 implements AbstractProductA
{
    public function usefulFunctionA(): string
    {
        return "The result of the product A2.";
    }
}

interface AbstractProductB
{
    /**
     * Product B is able to do its own thing...
     */
    public function usefulFunctionB(): string;

    /**
     * ...but it also can collaborate with the ProductA.
     *
     * The Abstract Factory makes sure that all products it creates are of the
     * same variant and thus, compatible.
     */
    public function anotherUsefulFunctionB(AbstractProductA $collaborator): string;
}

class ConcreteProductB1 implements AbstractProductB
{
    public function usefulFunctionB(): string
    {
        return "The result of the product B1.";
    }

    /**
     * The variant, Product B1, is only able to work correctly with the variant,
     * Product A1. Nevertheless, it accepts any instance of AbstractProductA as
     * an argument.
     */
    public function anotherUsefulFunctionB(AbstractProductA $collaborator): string
    {
        $result = $collaborator->usefulFunctionA();

        return "The result of the B1 collaborating with the ({$result})";
    }
}

class ConcreteProductB2 implements AbstractProductB
{
    public function usefulFunctionB(): string
    {
        return "The result of the product B2.";
    }

    /**
     * The variant, Product B2, is only able to work correctly with the variant,
     * Product A2. Nevertheless, it accepts any instance of AbstractProductA as
     * an argument.
     */
    public function anotherUsefulFunctionB(AbstractProductA $collaborator): string
    {
        $result = $collaborator->usefulFunctionA();

        return "The result of the B2 collaborating with the ({$result})";
    }
}


function clientCode(AbstractFactory $factory)
{
    $productA = $factory->createProductA();
    $productB = $factory->createProductB();

    echo $productB->usefulFunctionB() . "\n";
    echo $productB->anotherUsefulFunctionB($productA) . "\n";
}

// Testing
echo "Client: Testing client code with the first factory type:\n";
clientCode(new ConcreteFactory1());

echo "\n";

echo "Client: Testing the same client code with the second factory type:\n";
clientCode(new ConcreteFactory2());