February 28, 2017


layout: post title: Learn about Factory Method Design Pattern! categories:

  • blog

I would like to start with a somewhat formal description of what a factory method design pattern is.

the factory method pattern is a creational pattern that uses factory methods to deal with the problem of creating objects without having to specify the exact class of the object that will be created. This is done by creating objects by calling a factory method—either specified in an interface and implemented by child classes, or implemented in a base class and optionally overridden by derived classes—rather than by calling a constructor.

Read the above paragraph twice or thrice slowly until it starts to make some sense.


from abc import ABCMeta, abstractmethod
from enum import Enum

class Person(metaclass=ABCMeta):

    def get_name(self):
        raise NotImplementedError("You should implement this!")

class Villager(Person):
    def get_name(self):
        return "Village Person"

class CityPerson(Person):
    def get_name(self):
        return "City Person"

class PersonType(Enum):
    RURAL = 1
    URBAN = 2

class Factory:
    def get_person(self, person_type):
        if person_type == PersonType.RURAL:
            return Villager()
        elif person_type == PersonType.URBAN:
            return CityPerson()
            raise NotImplementedError("Unknown person type.")

factory = Factory()
person = factory.get_person(PersonType.URBAN)