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| Home : ASP.Net : Articles : Design Patterns Tutorial |
| Design Patterns Tutorial | Hits: 112 |
Description: Design patterns represent common software problems and the solutions to those problems in a formal manner. They were inspired by a book written by architect Christopher Alexander. Patterns were introduced in the software world by another book: "Design Patterns: Elements of Reusable Object-Oriented Software", by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. These people were nicknamed the "Gang of Four" for some mysterious reason. The Gang of Four describes 23 design patterns. With patterns you don't have to reinvent the wheel and get proven solutions for frequently encountered problems. Many books and articles have been written on this subject. This means that design patterns are becoming common knowledge, which leads to better communication. To summarize design patterns save time, energy while making your life easier.
Singleton
The singleton pattern deals with situations where only one instance of a class must be created. Take the case of a system administrator or superuser. This person has the right to do everything in a computer system. In addition we will also have classes representing normal users. Therefore we must ensure that these classes have no access to the super user constructor. The solution to this problem in C++ and Java is to declare the superuser constructor private. The superuser class itself has a private static attribute sysadmin, which is initialised using the class constructor. Now we get an instance of the super user class with a public static method that returns sysadmin. Here is the class diagram:
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| Resource Specification | | Platform: | .NET | | Date Added: | 05/12/2005 |
| Last Updated: | 05/12/2005 | | Author: | Faisal Khan |
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