Factory Method Design Pattern -PHP

Question

I am reading about factory design pattern, this pattern comes in 3 forms, simple factory, factory method and abstract factory.

what I understand, that's simple factory is not a design pattern, it just a type of encapsulate the object creation code in conjunction with if/switch statement or direct loading for the classes with exception if the class not exist!.

When I tried to move to factory method I can't find a clear enough example to defer it from simple factory.

could you guys give an example that's explain the factory method and how its defer from simple factory?

Thank you.

Answer 1

Simple Factory

A simple class with different methods (or one with a switch ) that is fully implemented with the creation logic. In PHP it can look like:

class AnimalFactory
{
    public function CreateAnimal($type)
    {
        if ($type == 'Dog') {
            return new Dog();
        } else {
            return new Cat();
        }
    }
}

If tommorow you'll have a new animal to support, you will have to change this class implementation. There are no subclasses here - this class knows everything about Animal creation.

Factory Method

Is what you use when you have a class that does some proccessing with Animal but doesn't know how or which Animal to create yet, therfore would like to have subclasses that will determine that. So we create a factory method that the sucblasses can override.

abstract Class MyAnimalProcess
{
    abstract function CreateAnimal();

    public function Process()
    {
        $animal = $this->CreateAnimal();
        ...
        ...
    }
}

class DogProcess extends MyAnimalProcess
{
    function CreateAnimal()
    {
        return new Dog();
    }
}

So, here you can have and abstract class that does something with an Animal , but let the subclasses of it determine which Animal it will be.

Abstract Factory

Take the factory method one step forward, and delegates the creation to another class - "the factory" class.
So it uses composition rather than inheritance.

abstract class AnimalFactory
{
    public abstract function CreatePet();
    public abstract function CreateWildAnimal();
}

class DogAnimalFactory extends AnimalFactory
{
    public function CreatePet()
    {
        return new Dog();
    }

    public function CreateWildAnimal()
    {
        return new AfricanWildDog();
    }
}

class CatAnimalFactory extends AnimalFactory
{
    public function CreatePet()
    {
        return new Cat();
    }

    public function CreateWildAnimal()
    {
        return new Tiger();
    }
}

class MyAnimalProcess
{
    function __construct($animalFactory) {
        $this->factory = $animalFactory;
    }

    public function ProcessPet()
    {
        $animal = $this->factory->CreatePet();
        ...
        ...
    }

    public function ProcessWild()
    {
        $animal = $this->factory->CreateWild();
        ...
        ...
    }
}

Answer 2

Maybe this will help, to make it more clear,
Abstract Factory is collection of the Factory Methods.

examples from real life:
Factory Method - plasticine/mold
Abstract Factory - cards factory