Question

I’m implementing an Statistics + Achievements system. Basically the structure is:

• An Achievement have many related Statistics, this relations must associate each Achievement with the required Statistics (and it value). For example the Achievement1 needs the Statistic1 with value 50 (or greater) and the Statistic2 with value 100 (or greater).
• Given an Statistic I need also know what are the related Achievements (in order to check them when the Statistic changes.

Both Stats and Achievements have an unique id.

My problem is I don´t know whats the best data(s) structure(s) for representing that. By the way I’m using:

SparseArray<HashMap<Statistic, Integer>> statisticsForAnAchievement;

For the first point where the index of the array is the Achievement ID and the HashMap contains the Statistic/TargetValue pairs. And a:

SparseArray<Collection<Achievement>> achievementsRelatedToAStatistic;

For the second point where the index is the StatisticID and the item is the collection of Achievements related.

Then I need to handle both objects keeping it coherence.

Is there an easier way of representing that? Thanks

Answer 1

As a Statistic(or a group of Statistics) describes an Achievement shouldn’t that/those Statistic/s be stored in the Achievement class? For example, an improved Achievement class:

public class Achievement {
    SparseArray<Statistic> mStatistics = new SparseArray<Statistic>();

    // to get a reference to the statisctics that make this achievement
    public SparseArray<Statistic> getStatics() {
        return mStatistics;
    }

    // add a new Statistic to these Achievement
    public void addStatistic(int statisticId, Statistic newStat) {
        // if we don't already have this particular statistic, add it
        // or maybe update the underlining Statistic?!?
        if (mStatistics.get(statisticId) == null) {
             mStatistic.add(newStat);
        }
    }

    // remove the Statistic
    public void removeStatistic(int statisticId) {
        mStatistic.delete(statisticId);
    }

    // check to see if this achievment has a statistic with this id
    public boolean hasStatistics(int statisticId) {
        return mStatistic.get(statisticId) == null ? false : true;
    }

    // rest of your code
}

Also, the Statistic class should store its target(the 50 value for Statistic1) value in it as a field.

An Achievement have many related Statistics, this relations must
associate each Achievement with the required Statistics (and it
value). For example the Achievement1 needs the Statistic1 with value
50 (or greater) and the Statistic2 with value 100 (or greater).

The statistics are already stored in the achievments so all you have to do is store an array/list of ids of the achievments(or the achievements them self) and with this you’ll have access to the statistics that made those achievements.

Given an Statistic I need also know what are the related Achievements
(in order to check them when the Statistic changes.

You would use the above array/list of achievements, iterate them and check to see if the achievement holds that particular Statistic:

ArrayList<Achievement> relatedAchievements = new ArrayList<Achievement>();
for (Achievement a : theListOfAchievments) {
     if (a.hasStatistics(targetStatistic)) {
          relatedAchievements.add(a); // at the end this will store the achievements related(that contain) the targetStatistic
     }
}

Another option is to have somewhere a static mapping that stores which achievements have a Statistic, mapping that would get updated each time one of the addStatictic or removeStatistic methods gets called.

Regarding your code, if you don’t need the Statistic object and are happy with just holding a reference to its id then you could improve the statisticsForAnAchievement with:

SparseArray<SparseIntArray> statisticsForAnAchievement;
// the index of the SparseArray is the Achievement's id
// the index of the SparseIntArray is the Statistic's id
// the value of the SparseIntArray is the Statistic's value