Skip to main content

Decorator Design Pattern


For this week's blog on Software Design, I decided to watch a short tutorial on one of the design patterns I didn't pick for a previous assignment. I picked Proxy Design pattern to cover before, and now I'm going back to learn about Decorator Design Pattern. It is only a thirteen minute video, so I won't be going as deep as I would had I picked it for the assignment. I am also going to talk about my reflections on it rather than create a tutorial, so I am not going to reteach it to the person reading this blog post.

The tutorial I chose was made by Derek Banas on YouTube. He used an example of a pizza parlor to illustrate the wrong way to code it by using inheritance. He shows the problem with this because you would have to create a very large number of subclasses for all your objects (in this case pizzas).

Composition, on the other hand, is a dynamic way of modifying objects. Instead of creating as many subclasses, you add functionality at run time. It has the benefits of inheritance, but is better to implement in many cases because it is more flexible. Instead of rewriting old code, you extend with new code.

This seems like a more intuitive way of doing things. In the example in the video, he uses the example of creating different kinds of pizza. If you were to design a menu for the same pizza place and there was twenty ingredients and different prices for each, it would make more sense to list the cost of the sizes “Small $5, Medium $7, etc.” and the prices of the toppings in a similar way, with Pepperoni and Sausage being 50¢ and 65¢ respectively. The customer would then choose the size and toppings and add all those together to get the total price.

It seems like the decorator does exactly this. It would seem silly for a pizza shop to list every permutation of toppings and sizes. It would make sense if there were only a handful of pizzas to choose from, but it does not make sense to do this if there are too many ways to list. Same with inheritance instead of decorator design pattern. The same logic is true with inheritance. This seems like an incredibly useful and versatile tool to use. I think learning about this will be incredibly invaluable for the future.

http://www.newthinktank.com/2012/09/decorator-design-pattern-tutorial/
Labels:

Comments

Post a Comment

Popular posts from this blog

Sprint 5 Retrospective (Capstone)

It is a shame that we are so close to the end of the semester. We were gaining so much momentum. It took us a while for us to get off the ground, but once we did, we never stopped gaining speed. I feel we will be able to keep this up through this last sprint. My hopes at the beginning of the semester for what we could accomplish were unrealistically high, but I am not disappointed with what we accomplished. We have not completed a full working component quite yet, but we are very close. I think our efforts are best spent finishing the one we are currently working on and doing it right. If we divided our efforts into starting something new, we run the risk of not fully completing anything. In the sage words of Ron Swanson, “Never half-ass two things. Whole-ass one thing.” If we are able to get the tabs working beautifully, I will be happy with our effort. I have felt that our group has done a phenomenal job this sprint and every sprint before with our communication. We have a few ...
Post a Comment
Read more

Testing: Like Destroying Sandcastles

https://joecolantonio.com/testtalks/223-testing-dream-journaling-smashing-sand-castles-with-noemi-ferrera/ In this blog for software quality assurance and testing, I decided to return to the “Test Talks” podcast, presented by Joe Colantonio, for another episode (#223). In it, he sat down with Noemi Ferrera, a software tester for a Chinese mobile gaming company to get her take on the subject. Noemi gave a few interesting metaphors that I appreciated for how to look at testing. In one, she gave the example of going to a movie where you had already read the book. It was different than how you imagined it while reading it, and testing is a way of making the “movie version” fit the way you envisioned it playing out.  The other metaphor for testing that she gave was, if you were children at the beach, the developers would be the ones building the sandcastles, whereas the testers would be the ones destroying them. I don’t know if that would be the most accurate way of lookin...
Post a Comment
Read more

Data Structures Primer

I've been a tutor for this past semester to students taking Introduction to Programming. Many who have come to my session are moving on to Data Structures next semester. They asked if they could have a primer as to what to expect. I have some resources that I have found helpful both while taking the course and tutoring it in the past. It will take me a little bit to compile a good list of those, but for now, here is a bare-bones list of topics of topics you might expect to see for a data structures course: Part 1: - Running time of code segments (Big-O Notation) - Abstract Data Type (ADT) - Interfaces (when to use "implements", cannot instantiate them, what inheritance is) - Superclass, subclass, method overriding/overloading - Abstract classes Part 2: - Binary Search Trees - Stacks (and its four methods — push, pop, peek, empty) - Linked list (single, double, circular) - Prefix and postfix notation (compare to infix) Part 3: - Min/Max Heap - Hash Table...
Post a Comment
Read more