Skip to main content

Refactoring To Patterns

I learned design patterns when I was in grad school. Later when I started work, I used some patterns, but some were never used, and their knowledge became rusty over the years. I thought it was time to refresh my knowledge of software design patterns, sometime last year.

Back then I was enamoured with the concept of web based learning (and I still am). I was also contemplating to take my Java workshops over the Internet. So instead of just re-reading the GOF book, I thought of taking a web based course on design patterns. This way I would learn what I needed to, and also get a hands on feel of how elearning works. When I Googled elearning and design patterns, I stumbled upon Industrial Logic's online course "Refactoring to patterns". Now the concept of refactoring to patterns is'nt just about learning design patterns. It involves understanding design patterns, but also involves identifying code smells (bad code), that should be refactored to use a design pattern. I was delighted. This course would not only help me refresh design patterns but also teach me something new. I registered for it.

I found the course to be very well made. The explanation of each design pattern started with some reading suggestions, typically from the GOF book and Joshua Kerievsky's excellent book - "Refactoring to patterns". After that there was a little conversation on that design pattern. This is really good, because after reading the text, I had many questions in my mind, and they were all answered by reading the conversation (which I am presuming Joshua must have had with participants of his course). Now that the theory had sunk in, the next step was to understand some code and refactor it to use the pattern. I could verify my solution by running the tests. The interesting thing here is that the tests not only verify that the code still works properly, but also verify if the refactoring uses the design pattern correctly. These tests make many assumptions, but they are very well written and do verify the solution correctly. Once you are done you can upload the solution. The course also has screencasts for the refactoring if you need any help. Finally there are some questions to reinforce the concepts.

I still have not completed all the patterns in the course, but have had a great learning experience with the stuff that I have completed.

In time to come web based learning will provide an excellent way for people to update their knowledge at a time, place, and pace of their convinience. The ability of the Internet to serve multimedia and enable collaboration is extremely powerful. I think we are just begining to scratch the surface if this potential for educational applications. The social web and the web of participation will bring several changes to the way we teach and learn. We will see many interesting eLearning content come up in future. Also, be on the lookout for educational podcasts and screencasts.
BTW, this is NOT a sponsored/paid post! ;-)

Notes: This text was originally posted on my earlier blog at http://www.adaptivelearningonline.net

Comments

Popular posts from this blog

My HSQLDB schema inspection story

This is a simple story of my need to inspect the schema of an HSQLDB database for a participar FOREIGN KEY, and the interesting things I had to do to actually inspect it. I am using an HSQLDB 1.8 database in one of my web applications. The application has been developed using the Play framework , which by default uses JPA and Hibernate . A few days back, I wanted to inspect the schema which Hibernate had created for one of my model objects. I started the HSQLDB database on my local machine, and then started the database manager with the following command java -cp ./hsqldb-1.8.0.7.jar org.hsqldb.util.DatabaseManagerSwing When I tried the view the schema of my table, it showed me the columns and column types on that table, but it did not show me columns were FOREIGN KEYs. Image 1: Table schema as shown by HSQLDB's database manager I decided to search on StackOverflow and find out how I could view the full schema of the table in question. I got a few hints, and they all pointed to ...

Commenting your code

Comments are an integral part of any program, even though they do not contribute to the logic. Appropriate comments add to the maintainability of a software. I have heard developers complain about not remembering the logic of some code they wrote a few months back. Can you imagine how difficult it can be to understand programs written by others, when we sometimes find it hard to understand our own code. It is a nightmare to maintain programs that are not appropriately commented. Java classes should contain comments at various levels. There are two types of comments; implementation comments and documentation comments. Implementation comments usually explain design desicisions, or a particularly intricate peice of code. If you find the need to make a lot of implementation comments, then it may signal overly complex code. Documentation comments usually describe the API of a program, they are meant for developers who are going to use your classes. All classes, methods and variables ...

Inheritance vs. composition depending on how much is same and how much differs

I am reading the excellent Django book right now. In the 4th chapter on Django templates , there is an example of includes and inheritance in Django templates. Without going into details about Django templates, the include is very similar to composition where we can include the text of another template for evaluation. Inheritance in Django templates works in a way similar to object inheritance. Django templates can specify certain blocks which can be redefined in subtemplates. The subtemplates use the rest of the parent template as is. Now we have all learned that inheritance is used when we have a is-a relationship between classes, and composition is used when we have a contains-a relationship. This is absolutely right, but while reading about Django templates, I just realized another pattern in these relationships. This is really simple and perhaps many of you may have already have had this insight... We use inheritance when we want to allow reuse of the bulk of one object in other ...