Realm Android 聚合子对象

Question

public class ChallengeDB extends RealmObject {

    @PrimaryKey
    private int challengeId;


    private String targetType;
    private RealmList<ChallengeTargetDB> ChallengeTargetDB;
    private boolean isTargetPerParticipant;
}



  public class ChallengeTargetDB extends RealmObject {
        @PrimaryKey
        private int targetId;
        private String targetName;
        private String description;
        private long targetValue;
        private int targetStep;
        private boolean isPassed;
}

我将这 2 个表链接如下，我需要获取特定挑战 ID 的最大“targetValue”值。

我写的查询如下

RealmResults<ChallengeDB> challengeDBs = realm.where(ChallengeDB.class)
                    .equalTo(WorkoutCashConstants.COLUMN_CHALLENGE_ID, challengeDB.getChallengeId()).findAll();

            long max = challengeDBs.max("ChallengeTargetDB.targetValue").longValue();

我起床结束异常如下

java.lang.IllegalArgumentException: Aggregates on child object fields are not supported: ChallengeTargetDB.targetValue

Answer 1

Realm 3.5.0+

public class ChallengeTargetDB extends RealmObject {
    @PrimaryKey
    private int targetId;
    private String targetName;
    private String description;
    private long targetValue;
    private int targetStep;
    private boolean isPassed;

    @LinkingObjects("ChallengeTargetDb")
    private final RealmResults<ChallengeDb> targetOfChallenge = null;
  }

然后

 RealmResults<ChallengeTargetDB> challengeDBs = realm.where(ChallengeTargetDB.class)
                .equalTo("targetOfChallenge." + WorkoutCashConstants.COLUMN_CHALLENGE_ID, challengeDB.getChallengeId()).findAll();

        long max = challengeDBs.max("targetValue").longValue();

Answer 2

正如例外所说，不支持链接对象字段上的聚合。您需要自己计算。

试试这个：

Number max = null;
for (ChallengeDB item : challengeDBs) {
    if (max == null) {
        max = item.ChallengeTargetDB.max();
    } else {
        Number tmp = item.ChallengeTargetDB.max();
        max = max.longValue() > tmp.longValue() ? max : tmp;
    }
}