Creating a bridge table equivalent realm class?

Question

I am designing a database which I am planning to implement on Android using Realm. I am still exploring and reading about using the library but I have one question that concerns me. Is it possible to implement a bridge table (see the diagram bellow) using Realm?

From what I read in the "Relationships" section in the docs link, I can use RealmList object to do many to many relationships. For example, for the "User_Activity" table. However, I an still unsure how to "convert" the database design into Realm class equivalent.

Answer 1

public class User extends RealmObject {
    @PrimaryKey
    private String userId;

    private String password;

    @Index
    private String username;

    private String paGoal; // ?

    private long maxInactivityInterval;

    private RealmList<UserActivity> userActivities;

    private Activity currentActivity; // optional
}

public class UserActivity extends RealmObject {
    @PrimaryKey
    private String userIdAndActivityIdAndDate; // userid_activityid_2017-01-23

    @Index
    private Date date;

    private long duration;

    private User user;

    @Index
    private String userId;

    private Activity activity;

    @Index
    private String activityId;
}

public class Activity extends RealmObject {
    @PrimaryKey
    private String activityId;

    @Index
    private String type;
}

I think this schema would work fine for you.