/ /

/ /

RealmAny - Java SDK

Atlas Device SDK 已弃用。有关详细信息，请参阅弃用页面。

版本 10.6.0 中的新增内容。

注意

新的Java SDK应用程序无法使用 RealmAny

新的 App Services应用将无法将数据模型与类型为 RealmAny的属性同步。

您可以使用RealmAny数据类型创建 Realm 对象字段，其中可以包含多种基础类型。您可以在RealmList 、 RealmDictionary或RealmSet字段中存储多个RealmAny实例。要更改RealmAny字段的值，请为新的RealmAny实例分配不同的基础值。在 Atlas App Services 后端对象模式中， RealmAny数据类型称为“混合”。 RealmAny字段可索引，但不能用作主键。

注意

RealmAny 类型兼容性

RealmAny 对象可以引用任何受支持的字段类型，但以下类型除外：

RealmAny
RealmList
RealmSet
RealmDictionary

使用

要创建RealmAny实例，请使用RealmAny.valueOf() 方法分配初始值，或使用RealmAny.nullValue()不分配任何值。 RealmAny实例不可变，就像String或Integer实例一样；如果要为RealmAny字段分配新值，则必须创建新的RealmAny实例。

警告

两个可能的 null RealmAny 值

RealmAny 实例始终可为null 。此外，实例可以包含类型为RealmAny.Type.NULL的值。

import com.mongodb.realm.examples.model.kotlin.Person;
import io.realm.RealmAny;
import io.realm.RealmObject;
public class Frog extends RealmObject {
    String name;
    RealmAny bestFriend;
    // realm-required empty constructor
    public Frog() {}
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public RealmAny getBestFriend() { return bestFriend; }
    public void setBestFriend(RealmAny bestFriend) { this.bestFriend = bestFriend; }
    public String bestFriendToString() {
        switch(bestFriend.getType()) {
            case NULL: {
                return "no best friend";
            }
            case STRING: {
                return bestFriend.asString();
            }
            case OBJECT: {
                if (bestFriend.getValueClass().equals(Person.class)) {
                    Person person = bestFriend.asRealmModel(Person.class);
                    return person.getName();
                }
            }
            default: {
                return "unknown type";
            }
        }
    }
}

  Frog frog = realm.createObject(Frog.class);
  frog.setName("Jonathan Livingston Applesauce");
  // set RealmAny field to a null value
  frog.setBestFriend(RealmAny.nullValue());
  Log.v("EXAMPLE", "Best friend: " + frog.bestFriendToString());
  // possible types for RealmAny are defined in RealmAny.Type
  Assert.assertTrue(frog.getBestFriend().getType() == RealmAny.Type.NULL);
  // set RealmAny field to a string with RealmAny.valueOf a string value
  frog.setBestFriend(RealmAny.valueOf("Greg"));
  Log.v("EXAMPLE", "Best friend: " + frog.bestFriendToString());
  // RealmAny instances change type as you reassign to different values
  Assert.assertTrue(frog.getBestFriend().getType() == RealmAny.Type.STRING);
  // set RealmAny field to a realm object, also with valueOf
  Person person = new Person("Jason Funderburker");
  frog.setBestFriend(RealmAny.valueOf(person));
  Log.v("EXAMPLE", "Best friend: " + frog.bestFriendToString());
  // You can also extract underlying Realm Objects from RealmAny with asRealmModel
  Person bestFriendObject = frog.getBestFriend().asRealmModel(Person.class);
  Log.v("EXAMPLE", "Best friend: " + bestFriendObject.getName());
  // RealmAny fields referring to any Realm Object use the OBJECT type
  Assert.assertTrue(frog.getBestFriend().getType() == RealmAny.Type.OBJECT);
  // you can't put a RealmList in a RealmAny field directly,
  // ...but you can set a RealmAny field to a RealmObject that contains a list
  GroupOfPeople persons = new GroupOfPeople();
  // GroupOfPeople contains a RealmList of people
  persons.getPeople().add("Rand");
  persons.getPeople().add("Perrin");
  persons.getPeople().add("Mat");
  frog.setBestFriend(RealmAny.valueOf(persons));
  Log.v("EXAMPLE", "Best friend: " +
          frog.getBestFriend().asRealmModel(GroupOfPeople.class).getPeople().toString());

import io.realm.RealmAny
import io.realm.RealmObject
open class Frog(var bestFriend: RealmAny? = RealmAny.nullValue()) : RealmObject() {
    var name: String? = null
    open fun bestFriendToString(): String {
        if (bestFriend == null) {
            return "null"
        }
        return when (bestFriend!!.type) {
            RealmAny.Type.NULL -> {
                "no best friend"
            }
            RealmAny.Type.STRING -> {
                bestFriend!!.asString()
            }
            RealmAny.Type.OBJECT -> {
                if (bestFriend!!.valueClass == Person::class.java) {
                    val person = bestFriend!!.asRealmModel(Person::class.java)
                    person.name
                }
                "unknown type"
            }
            else -> {
                "unknown type"
            }
        }
    }
}

val frog = realm.createObject(Frog::class.java)
frog.name = "George Washington"
// set RealmAny field to a null value
// set RealmAny field to a null value
frog.bestFriend = RealmAny.nullValue()
Log.v("EXAMPLE", "Best friend: " + frog.bestFriendToString())
// possible types for RealmAny are defined in RealmAny.Type
Assert.assertEquals(frog.bestFriend?.type, RealmAny.Type.NULL)
// set RealmAny field to a string with RealmAny.valueOf a string value
frog.bestFriend = RealmAny.valueOf("Greg")
Log.v("EXAMPLE", "Best friend: " + frog.bestFriendToString())
// RealmAny instances change type as you reassign to different values
Assert.assertEquals(frog.bestFriend?.type, RealmAny.Type.STRING)
// set RealmAny field to a realm object, also with valueOf
val person = Person("Jason Funderburker")
frog.bestFriend = RealmAny.valueOf(person)
Log.v("EXAMPLE", "Best friend: " + frog.bestFriendToString())
// You can also extract underlying Realm Objects from RealmAny with asRealmModel
val bestFriendObject = frog.bestFriend?.asRealmModel(Person::class.java)
Log.v("EXAMPLE", "Best friend: " + bestFriendObject?.name)
// RealmAny fields referring to any Realm Object use the OBJECT type
Assert.assertEquals(frog.bestFriend?.type, RealmAny.Type.OBJECT)
// you can't put a RealmList in a RealmAny field directly,
// ...but you can set a RealmAny field to a RealmObject that contains a list
val persons = GroupOfPeople()
// GroupOfPeople contains a RealmList of people
persons.people.add("Rand")
persons.people.add("Perrin")
persons.people.add("Mat")
frog.bestFriend = RealmAny.valueOf(persons)
Log.v("EXAMPLE", "Best friend: " +
        frog.bestFriend?.asRealmModel(GroupOfPeople::class.java)
                ?.people.toString())

查询

您可以像查询任何其他数据类型一样查询RealmAny字段。仅适用于某些类型的操作符（例如字符串操作符和算术操作符）会忽略不包含该类型的值。否定此类操作符会匹配不包含该类型的值。类型查询匹配底层类型，而不是RealmAny 。算术运算符隐式转换数值以进行跨类型比较。

通知

要订阅对RealmAny字段的更改，请使用RealmObject.addChangeListener 封闭对象的方法。您可以使用ObjectChangeSet参数来确定RealmAny字段是否已更改。

AtomicReference<Frog> frog = new AtomicReference<Frog>();
realm.executeTransaction(r -> {
        frog.set(realm.createObject(Frog.class));
        frog.get().setName("Jonathan Livingston Applesauce");
});
RealmObjectChangeListener<Frog> objectChangeListener =
        new RealmObjectChangeListener<Frog>() {
    @Override
    public void onChange(@NotNull Frog frog, @Nullable ObjectChangeSet changeSet) {
        if (changeSet != null) {
            Log.v("EXAMPLE", "Changes to fields: " +
                    Arrays.toString(changeSet.getChangedFields()));
            if (changeSet.isFieldChanged("best_friend")) {
                Log.v("EXAMPLE", "RealmAny best friend field changed to : " +
                        frog.bestFriendToString());
            }
        }
    }
};
frog.get().addChangeListener(objectChangeListener);
realm.executeTransaction(r -> {
    // set RealmAny field to a null value
    frog.get().setBestFriend(RealmAny.nullValue());
    Log.v("EXAMPLE", "Best friend: " + frog.get().bestFriendToString());
    // set RealmAny field to a string with RealmAny.valueOf a string value
    frog.get().setBestFriend(RealmAny.valueOf("Greg"));
});

var frog: Frog? = null
realm.executeTransaction { r: Realm? ->
    frog = realm.createObject(Frog::class.java)
    frog?.name = "Jonathan Livingston Applesauce"
}
val objectChangeListener
        = RealmObjectChangeListener<Frog> { frog, changeSet ->
    if (changeSet != null) {
        Log.v("EXAMPLE", "Changes to fields: " +
                changeSet.changedFields)
        if (changeSet.isFieldChanged("best_friend")) {
            Log.v("EXAMPLE", "RealmAny best friend field changed to : " +
                    frog.bestFriendToString())
        }
    }
}
frog?.addChangeListener(objectChangeListener)
realm.executeTransaction { r: Realm? ->
    // set RealmAny field to a null value
    frog?.bestFriend = RealmAny.nullValue()
    Log.v("EXAMPLE", "Best friend: " + frog?.bestFriendToString())
    // set RealmAny field to a string with RealmAny.valueOf a string value
    frog?.bestFriend = RealmAny.valueOf("Greg")
}

后退

集

来年

Enums