A UnitOfWork is a business transaction. Not necessarily a technical transaction (db transaction) but often tied to technical transactions. In the enterprise application patterns it is defined as Maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems. It does not define … Read more
There’s a book in Martin Fowler’s Signature Series called Refactoring Databases. That provides a list of techniques for refactoring databases. I can’t say I’ve heard a list of database patterns so much. I would also highly recommend David C. Hay’s Data Model Patterns and the follow up A Metadata Map which builds on the first … Read more
Let’s explain the strategy pattern the easy way: You have a class Car() with a method run(), so you use it this way in a pseudo language: mycar = new Car() mycar.run() Now, you may want to change the run() behavior on the fly, while the program is executing. For example, you might want to … Read more
Utility classes aren’t exactly evil, but they can violate the principles that compose a good object-oriented design. In a good object-oriented design, most classes should represent a single thing and all of its attributes and operations. If you are operating on a thing, that method should probably be a member of that thing. However, there … Read more
I give you dependency injection for five-year-olds. When you go and get things out of the refrigerator for yourself, you can cause problems. You might leave the door open, you might get something Mommy or Daddy doesn’t want you to have. You might even be looking for something we don’t even have or which has … Read more
I believe it should be Command design pattern. Here is article about multilevel Undo/Redo with Command pattern. EDIT: Here is second about multilevel Undo/Redo with Memento pattern. So probably it can be done with both.
Singletons are like communism: they both sound great on paper, but explode with problems in practice. The singleton pattern places a disproportionate emphasis on the ease of accessing objects. It completely eschews context by requiring that every consumer use an AppDomain-scoped object, leaving no options for varying implementations. It embeds infrastructure knowledge in your classes … Read more
There’s a combination of Federico’s and John’s answers. When: —-Shape— / \ Rectangle Circle / \ / \ BlueRectangle RedRectangle BlueCircle RedCircle Refactor to: —-Shape— Color / \ / \ Rectangle(Color) Circle(Color) Blue Red
I asked a similar question, but where possible I try to copy the names already in the .NET framework, and I look for ideas in the Java and Android frameworks. It seems Helper, Manager, and Util are the unavoidable nouns you attach for coordinating classes that contain no state and are generally procedural and static. … 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