Case statements represent a bad code smell. Case statements that switch on a type-code are often duplicated throughout a program. The purpose of this example is to demonstrate the steps involved in a replace-case-with-strategy refactoring.
The context of the example is based around a mock football (soccer) game. The specific area of focus being the process a match official (Referee) goes through when determining what action should be taken in response to a game incident (Foul).
The code prior to the refactoring can be inspected in following commit: 0906a62. The key focus of our refactoring will be the #make_decision method of the Soccer::Referee class which contains a case statement that switches on incident.type.
The first refactoring that is applied is to extract each branch of the case statement to a method. This refactoring can be seen by comparing commit 0906a62 with 4fcb773
The last step is to extract these branch methods to a new module (Soccer::RefereeStrategies). These methods are defined as Procs so that they can act as drop in strategies. This refactoring can be seen by comparing commit 4fcb773 with 6b65d72.