Daily Reading - Tuesday, July 02 2013

A study on design patterns and software quality at the University of Montreal (2008) found that design patterns in practice do not always improve code quality, reusability and expandability; and often makes code harder to understand. Some patterns are better than others: Composite makes code easier to follow and easier to change. Abstract Factory makes code more modular and reusable, but at the expense of understandability. Flyweight makes code less expandable and reusable, and much harder to follow. Most developers don’t recognize or understand the Visitor pattern. Observer can be difficult to understand as well, although it does make the code more flexible and extendible. Chain of Responsibility makes code harder to follow, and harder to change or fix safely. And Singleton, of course, while simple to recognize and understand, can make code much harder to change.

Whether you’re designing and writing new code, or changing code, or refactoring code, the best advice is:

Don’t use patterns unless you need to.

Don’t use patterns that you don’t fully understand.

Don’t expect that whoever is going to work on the code in the future to recognize and understand the patterns that you used – stick to common patterns, and make them explicit in comments where you think it is important or necessary.

When you’re changing code, take some time to look for and understand the patterns that might be in place, and decide whether it is worth preserving (or restoring) them: whether doing this will really make the code better and more understandable.

Browser Link in VS 2013
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Five Patterns to Help You Tame Asynchronous JavaScript

Callbacks
Observer Pattern
Messaging
Promises
Finite State Machines