This is a postmortem of the project. In the UMLs section an overview of the design is presented. The rest of the document discusses design decisions, the new requirements and some other relevant information.
This section presents UMLs of the design. To keep things simple it only shows the more important methods and fields.
This is an overview of the MVC model. Simulator acts as the Model in this case.
This is an overview of the Model.
This section discusses some of the key design descisions.
Countries keep their neighbors in a list and the list is set at initialization. They don't query the Simulator for their neighbors. They didn't keep a handle to the Simulator until air travel was introduced.
All of the information displayed comes from a subclass in Country called HealthStats that outgrew its original scope. Simulator (Model) goes through the list of countries and collects the stat objects and then passes it to the Controller at the end of each day. Originally it kept only the health related stats, however as development went on it became the core data for the View, even passing the country name and move counts. View processes the stats and generates various charts. It is limited in the sense that it doesn't track individual Humans actions.
The initial decision to make SimulationRules a singleton was made to keep the rules in a single class that is accessible from anywhere, instead of passing a rules object around or having a handle to the Simulator object everywhere to be able to query the rules. However, this limits how many Simulator objects can be run. With a singleton they have to share the rules.
SimulationRules also has a random number generator and is used for "dice throw" methods.
Not all HealthState subclasses count days (Healthy, Dead, Super). The ones that do repeat the day counting code. Maybe there could've been another level of abstract class that did the day counting.
There are type queries for all HealthState subclasses like isHealthy, isDead. Also for Doctor class as isDoctor. It was made this way for easier stat collecting but adding these queries for all was a bit tedious.
Human and Doctor also query isDead to not take non healthstate related actions.
- MVC pattern used to establish interaction in between simulator and user interface.
- Simulation rules are kept in a SimulationRules object, which uses the Singleton pattern.
- On each day, simulator delegates daily operations into Country objects and country objects delegates to Human objects.
- Human objects delegates health related processes to HealthState objects; where HealthState objects are allowed to change health field of Humans -State pattern.
This section discusses the changes made for the new requirements.
Related Change on GitHub (Link)
This change was fairly simple as it only required changing methods that calculated the neighbor indices.
Related Change on GitHub (Link)
This change introduced a new subclass for HealthState. For Human constructor to start with Super we modified the constructor from a isInfected boolean to a type enum. However the enum was later removed for the Doctor change below as it complicated the initialization.
Related Change on GitHub (Link)
Doctor was implemented as a subclass of Human and was fairly simple. It has its
own passDay that runs super.passDay() in the end.
A "isVaccineCandidate" was added to HealthState abstract class to determine targets.
The ugly part was the populate method of Simulator. This is because the rules indicate doctor and regular Humans to be unrelated to the healthy, infected and super percentages. So we made a decision to just change the constructor to initiate Humans and Doctors first with the default constructors and then assign initial health states. Otherwise, assigning overlapping Doctor/Human and Healthy/Infected/Super percentages was going to be complicated.
Related Change on GitHub (Link)
This change required us to pass a Simulator handle to Country for querying the list of countries. Previously, they only had a list of neighbors.
We added another dice throw method to the SimulationRules object.
This section discusses some of the bugs that were caught late in development.
Different map sizes weren't tested so "rows" related "cols" bug in neighbor association was caught late.
If countries were neighboring themselves due to round world rules, Human objects considered their own country a move candidate. In this case they were added to their population lists multiple times breaking the population calculations.
HealthState and Human's passDay actions unrelated to the health state are kept
separate. So it was easy to miss Dead state check for Doctor as it was doing
vaccination in it's own passDay and then just calling super.passDay().