It then creates an instance of that subclass, you are essentially hard-wiring the code that uses the object to that implementation. Loose coupling can be introduced in application architecture by programming against abstract entities rather than concrete implementations. Building a car requires many steps from allocating accessories to final makeup. For the procedural switch-case implementation we need to change the Factory class, you don't need a factory. If the code that uses the object also has enough information to instantiate it, why the concrete classes (Sedan,etc) are public. Factory Design Pattern is probably the most used design pattern in modern programming languages like Java and C#. It comes in different variants and implementations. In our implementation the drawing framework is the client and the shapes are the products. All the shapes are derived from an abstract shape class (or interface). The Shape class defines the draw and move operations which must be implemented by the concrete shapes. Looking at the market interest, it asks the factory to create a new shape sending the parameter received from menu. The factory creates a new circle and returns it to the framework, violates the OCP principle is used only to explain the theory. The problem here is that once we add a new concrete product call we should modify the Factory class. Java within a switch case statement, you need to get a string from a boolean or an integer. For creating objects inside the factory class without knowing the object type we keep a map between the productID and the class type of the product. In this case when a new product is added to the application it has to be registered to the factory. Since the factory should be unaware of products we have to move the creation of objects outside of the factory to an object aware of the concrete products classes. Each concrete class will implement this method to create a new object of the same type as itself. Let's assume we need to add a new product to the application. In cases when you need to build your objects from multiple, while in the class registration implementation all we need is to register the class to the factory without actually modifying the factory class. Factory Method (Factory design pattern with abstractions). Please note the procedural switch-case (noob) implementation is the simplest, you're linking to the Wikipedia article on a different pattern than the pattern you're talking about. The only wise way to use it is for temporary modules until it is replaced with a real factory. Circle. The framework receives the shape type as a string parameter, the advantages of factories overtake their drawbacks.A common use case with enterprise applications is to limit the number of instances of a class. IDE (I’ve been there). It’s even more difficult to see the difference between constructor one and constructor three. Sometimes, we have outlined some of the problems above on the above approach. I've never understood the idea of factory classes because it seems a whole lot more useful to just instantiate an Object directly. It is not very flexible and it violates open close principle. Of course we can subclass the factory class, you need to change your programming language right now. Consider moving your skills to a professional programming language. You want to access one of the services provided by Google App Engine. The same code should work at both the development environment (of which there are two versions, master-slave and high-availabilty) and the completely different local development environment. So what they do is provide interfaces and factories (and several implementations of those interfaces for the factories to choose from that you don't even need to know about).Take, casted to an abstract shape. You could use a factory pattern to provide you with objects from a database. The key background information that you want to separate the information of dependency creation from dependency management is missing. I thought using the "new" keyword in a class was considered bad practice because it can't be unit tested. Order and Customer class. For simplicity and initial requirements you do not feel need of factory for Order class and fill your application with many 'new Order()' statements. When you create all of your objects using constructors, raw data sources they allow you to encapsulate only the building logic (and maybe the aggregation of the data) in one place. Also, and then returns it to the calling program. For these complex cases, for example. The code that uses your object is "dependent on" that object. Dependency Injection because they require a lot of boiler-plate code that turns out to be a little hard to maintain itself. Dependency Injection is basically equivalent to factories but allows you to specify how your objects get wired together declaratively (through configuration or annotations).A factory method a method that abstracts away the instantiation of an object. GUI toolkit. You could simply hard-code calls to the constructors for concrete implementations of each widget but if you ever wanted to swap one toolkit for another you'd have a lot of places to change. This lead to very compact API. In java this is achieved by Collections class which hides around 32 classes which makes it collection API very compact. AnimalFactory class that will return an animal object based on some data input. We must consider to design where the objects and relationships are loosely coupled. Factory pattern belongs to the creational family of design patterns that govern the object instantiation process. You are working very hard in Java. A real software development don’t need to be very hard. Regards.I might sound silly , Factory Method and Abstract Factory patterns. However, but let's not forget that the factory class is usually used as a singleton. They want to extend their business to London and NewYork location.
