Motivation for Simple Factory and Factory Method Pattern

Question

I know there are a lot of questions out there about differences of different factory patterns, but the answers are so different and confusing. The books that i read use uncl

Answer 1

You are seeing examples of two styles of factory method because there are two completely separate situations where they are appropriate.

The first type - which seems to coincide with what you are being led to call a simple factory comes about when you have a relatively complicated object that can be difficult to create because of it's complexity.

The classic example here is the Pizza class which has a PizzaConstructor class (or some similar name) where much of the clevers required to build the Pizza object is encoded into the Constructor.

There's a nice discussion here but the salient point is that this form puts the clevers of how to construct the Pizza in a Factory rather than bogging down the Pizza class.

With this technique you can make constructor code that is much clearer than it would normally be.

Pizza pizza = PizzaFactory.addTopping(Cheese)
    .addTopping(Anchovies)
    .thickCrust()
    .stuffedCrust(Gruyere)
    .stoneBaked()
    .buildPizza();

The second situation for the use of factories is when you need your class to be able to actually make objects of a supplied type. This is difficult without the user supplying a factory mechanism for you to use. The user then supplies a factory mechanism of some sort, perhaps a factory object or maybe they extend your abstract class and provide a concrete constructor method.