Android领域迁移:添加新领域列表列

Question

我正在使用Realm v0.80.1,我正在尝试为我添加的新属性编写迁移代码.该房产是RealmList.我不知道如何正确添加新列或设置一个值.

我有:customRealmTable.addColumn(,"list");

一旦正确添加了列,我将如何设置list属性的初始值？我想做的事情如下:

customRealmTable.setRealmList(newColumnIndex,rowIndex,new RealmList <>());

Answer 1

从Realm v1.0.0开始(也许之前),你可以简单地调用RealmObjectSchema#addRealmListField(String, RealmObjectSchema)(链接到javadoc)来实现这一点.例如,如果您尝试向类中添加permissions类型字段,则RealmList<Permission>需要User编写:

if (!schema.get("User").hasField("permissions")) {
    schema.get("User").addRealmListField("permissions", schema.get("Permission"));
}

也有在领域的迁移文档的例子在这里.addRealmListField为方便起见,这里是完整的javadoc :

/**
 * Adds a new field that references a {@link RealmList}.
 *
 * @param fieldName  name of the field to add.
 * @param objectSchema schema for the Realm type being referenced.
 * @return the updated schema.
 * @throws IllegalArgumentException if the field name is illegal or a field with that name already exists.
 */

Answer 2

您可以在此处的示例中看到添加RealmList属性的示例:https://github.com/realm/realm-java/blob/master/examples/migrationExample/src/main/java/io/realm/examples/realmmigrationexample /model/Migration.java#L78-L78

相关代码是此部分:

   if (version == 1) {
            Table personTable = realm.getTable(Person.class);
            Table petTable = realm.getTable(Pet.class);
            petTable.addColumn(ColumnType.STRING, "name");
            petTable.addColumn(ColumnType.STRING, "type");
            long petsIndex = personTable.addColumnLink(ColumnType.LINK_LIST, "pets", petTable);
            long fullNameIndex = getIndexForProperty(personTable, "fullName");

            for (int i = 0; i < personTable.size(); i++) {
                if (personTable.getString(fullNameIndex, i).equals("JP McDonald")) {
                    personTable.getRow(i).getLinkList(petsIndex).add(petTable.add("Jimbo", "dog"));
                }
            }
            version++;
        }