by Paula Muldoon (Makers Academy remote April 2017 cohort)
I spent two days working on refactoring this legacy code. I used duck typing and inheritance to refactor the nested if/else conditionals to make a clean and easily extensible program.
Note: in my solution, I decided to edit the
Item class slightly, to catch errors upon instantation and also to remove the attr_accessor. However, the
item-class branch has the solution with the
Item class intact, as per the goblin's instructions below. The
Sulfura class has been removed in master branch, as it is redundant (all necessary behaviour is contained within the superclass
For further information on duck typing, please see Sandi Metz's POODR, chapter 5, "Reducing Costs with Duck Typing."
*"Hi and welcome to team Gilded Rose. As you know, we are a small inn with a prime location in a prominent city run by a friendly innkeeper named Allison. We also buy and sell only the finest goods. Unfortunately, our goods are constantly degrading in quality as they approach their sell by date.
We have a system in place that updates our inventory for us. It was developed by a no-nonsense type named Leeroy, who has moved on to new adventures. Your task is to add the new feature to our system so that we can begin selling a new category of items. First an introduction to our system:
All items have a SellIn value which denotes the number of days we have to sell the item.
All items have a Quality value which denotes how valuable the item is.
At the end of each day our system lowers both values for every item. Pretty simple, right? Well this is where it gets interesting:
- Once the sell by date has passed, Quality degrades twice as fast
- The Quality of an item is never negative
- “Aged Brie” actually increases in Quality the older it gets
- The Quality of an item is never more than 50
- “Sulfuras”, being a legendary item, never has to be sold and does not decrease in Quality
- “Backstage passe”, like aged brie, increases in Quality as its SellIn value approaches; Quality increases by 2 when there are 10 days or less and by 3 when there are 5 days or less but Quality drops to 0 after the concert
We have recently signed a supplier of conjured items. This requires an update to our system:
- “Conjured” items degrade in Quality twice as fast as normal items
Feel free to make any changes to the UpdateQuality method and add any new code as long as everything still works correctly. However, do not alter the Item class or Items property as those belong to the goblin in the corner who will insta-rage and one-shot you as he doesn’t believe in shared code ownership (you can make the UpdateQuality method and Items property static if you like, we’ll cover for you)."*
View the repository here on GitHub
Clone the repo. Then:
To run the tests
See the spreadsheet of tests