Guidelines for Choosing and Applying Design Pattern

There are so many design patterns to choose from, so how do you identify which one is appropriate for your problem? To know which design pattern to use and how to apply the solution template to your specific problem, it’s important to understand these guidelines.

➤➤ Patterns can’t be applied without knowing about them. The first important step is to expand your knowledge and study patterns and principles both in the abstract and concrete form. You can implement a pattern in many ways. The more you see different implementations of patterns, the more you will understand the intent of the pattern and how a single pattern can have varying implementations.

➤➤ Do you need to introduce the complexity of a design pattern? It’s common for developers to try to use a pattern to solve every problem. You always need to weigh the upfront time needed to implement a pattern for the benefit that it’s going to give. Remember the KISS principle: Keep It Simple, Stupid.

➤➤ Generalize your problem; identify the issues you’re facing in a more abstract manner. Remember that design patterns are high-level solutions; try to abstract your problem, and don’t focus too hard on the details of your specific issue. Try to keep a list of intent of each pattern and principle in your implementation for reference.

➤➤ Look at patterns of a similar nature and patterns in the same group. Just because you have used a pattern before doesn’t mean it will always be the correct pattern choice when solving a problem.

➤➤ Look at what will likely change with your application and encapsulate what varies. If you know that a special offer discount algorithm will change over time, look for a pattern that will help you change it without impacting the rest of your application.

➤➤ After you have chosen a design pattern, ensure that you use the language of your pattern along with the language of the domain when naming the participants in a solution. For example, if you are using the strategy pattern to provide a solution for costing various shipping couriers, name them accordingly, such as USPSCostStrategy. By using the pattern’s common vocabulary along with the language of your domain, you will immediately make your code more readable and understandable to other developers with patterns knowledge.
When it comes to design patterns, there is no substitute for studying.  A great learning exercise is to try to identify patterns in the .NET Framework. For example, the ASP.NET Cache uses the Singleton pattern; creating a new Guid uses the Factory pattern; the .NET 2 XML classes use the Factory pattern.

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Author: Shahzad Khan

Software developer / Architect