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
When the FragmentPagerAdapter adds a fragment to the FragmentManager, it uses a special tag based on the particular position that the fragment will be placed. FragmentPagerAdapter.getItem(int position) is only called when a fragment for that position does not exist. After rotating, Android will notice that it already created/saved a fragment for this particular position and … Read more
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
What is Inversion of Control?
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
Singletons have very little – if not to say no – use in PHP. In languages where objects live in shared memory, Singletons can be used to keep memory usage low. Instead of creating two objects, you reference an existing instance from the globally shared application memory. In PHP there is no such application memory. … Read more
Difference between static class and singleton pattern?
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
A bit decent web application consists of a mix of design patterns. I’ll mention only the most important ones. Model View Controller pattern The core (architectural) design pattern you’d like to use is the Model-View-Controller pattern. The Controller is to be represented by a Servlet which (in)directly creates/uses a specific Model and View based on … Read more
Another option is to use the +(void)initialize method. From the documentation: The runtime sends initialize to each class in a program exactly one time just before the class, or any class that inherits from it, is sent its first message from within the program. (Thus the method may never be invoked if the class is … Read more