同一类的多个领域表 [英] Multiple Realm Tables of same Class

问题描述

我有一个RealmObject类.我想要同一个类的多个表.我可以在单个Realm(数据库)中做到这一点，还是需要多个Realms(每个Realm一个表).

I have a RealmObject Class. I want multiple tables of the same class. Can I do that in a single Realm(Database) or I need to have multiple Realms(One table per each Realm).

如果必须有多个Realms，那么Realm切换过程有多快?

If it has to be multiple Realms, how fast is the Realm switching process?

推荐答案

我想要同一个类的多个表.

I want multiple tables of the same class.

那么您有两个合理的选择:

Well you have two reasonable options:

1.)添加一个鉴别符字段，该字段确定当前对象实例属于哪个表"

1.) add a discriminator field that determines which "table" this current object instance belongs to

public class MyObject extends RealmObject {
    @PrimaryKey
    private String tableAndId;

    @Index
    private String table;

    @Index
    private long id;

    // getters, setters
}

然后您可以查询每个表":

Then you can query "per table":

RealmResults<MyObject> results = realm.where(MyObject.class)
                                      .equalTo(MyObjectFields.TABLE, "tableA")
                                      .findAll();

2.)使用DynamicRealm动态创建所需的任何表，并通过RealmSchema手动创建模式.

2.) create any table you want dynamically using DynamicRealm and manual creation of the schema via the RealmSchema.

DynamicRealm dynamicRealm = DynamicRealm.getInstance(config);
RealmSchema schema = dynamicRealm.getSchema();
RealmObjectSchema objectSchema;
if(!schema.contains("MyObject_Table_A")) {
    objectSchema = schema.create("MyObject_Table_A");
    objectSchema.addField("id", long.class, FieldAttribute.PRIMARY_KEY);
    objectSchema.addField("created", Date.class, FieldAttribute.INDEXED);
    //...
} else {
    objectSchema = schema.get("MyObject_Table_A");
}

然后您可以写入动态领域:

And then you can write into the dynamic realm:

dynRealm.executeTransaction(new DynamicRealm.Transaction() {
    @Override
    public void execute(DynamicRealm dynRealm) {
        DynamicRealmObject dynObj = dynRealm.where("MyObject_Table_A")
                                            .equalTo("id", id)
                                            .findFirst();
        if(dynObj == null) {
            dynObj = dynRealm.createObject("MyObject_Table_A", id);
        }
        dynObj.setDate("created", new Date());
    }
});

---

每个表也可以有一个新配置，但这听起来像是一个不合理的选择，所以我什至不想提它.

---

You can also have a new configuration per table, but that sounds like an unreasonable option, so I barely even want to mention it.

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