I don’t really see the need, as a module with functions (and not a class) would serve well as a singleton. All its variables would be bound to the module, which could not be instantiated repeatedly anyway. If you do wish to use a class, there is no way of creating private classes or private … Read more
With the Factory pattern, you produce instances of implementations (Apple, Banana, Cherry, etc.) of a particular interface — say, IFruit. With the Abstract Factory pattern, you provide a way for anyone to provide their own factory. This allows your warehouse to be either an IFruitFactory or an IJuiceFactory, without requiring your warehouse to know anything … Read more
On my quest for the truth I discovered that there are actually very few “acceptable” reasons to use a Singleton. One reason that tends to come up over and over again on the internets is that of a “logging” class (which you mentioned). In this case, a Singleton can be used instead of a single … Read more
In the context of the repository pattern, aggregate roots are the only objects your client code loads from the repository. The repository encapsulates access to child objects – from a caller’s perspective it automatically loads them, either at the same time the root is loaded or when they’re actually needed (as with lazy loading). For … Read more
When using a factory your code is still actually responsible for creating objects. By DI you outsource that responsibility to another class or a framework, which is separate from your code.
The Difference Between The Two The main difference between a “factory method” and an “abstract factory” is that the factory method is a method, and an abstract factory is an object. I think a lot of people get these two terms confused, and start using them interchangeably. I remember that I had a hard time … Read more
It would be a lot nicer if javascript had namespaces built in, but I find that organizing things like Dustin Diaz describes here helps me a lot. var DED = (function() { var private_var; function private_method() { // do stuff here } return { method_1 : function() { // do stuff here }, method_2 : … Read more
Below are some reasons arguing for the use of the pattern and example code in Java, but it is an implementation of the Builder Pattern covered by the Gang of Four in Design Patterns. The reasons you would use it in Java are also applicable to other programming languages as well. As Joshua Bloch states … Read more
Use __new__ when you need to control the creation of a new instance. Use __init__ when you need to control initialization of a new instance. __new__ is the first step of instance creation. It’s called first, and is responsible for returning a new instance of your class. In contrast, __init__ doesn’t return anything; it’s only … Read more
You can find an overview of a lot of design patterns in Wikipedia. It also mentions which patterns are mentioned by GoF. I’ll sum them up here and try to assign as many pattern implementations as possible, found in both the Java SE and Java EE APIs. Creational patterns Abstract factory (recognizeable by creational methods … Read more