android - 使用 RealmMigration 在 Realm Android 中将数据类型从 String 更改为 Long

Question

final RealmObjectSchema customerSchema = schema.get("Customer");
customerSchema.removeField("creditPeriod")
    .addField("creditPeriod", Long.class);

以上是我用于领域迁移的代码。我删除了以前是字符串的已经存在的字段，然后在迁移代码和 Pojo.class 中添加了相同的字段来更改其数据类型

Answer 1

下面我刚刚提到了一个使用@christian-melchior 评论中提到的示例将字段类型从 String 迁移到 int 的示例

public class DataMigration implements RealmMigration {
    @Override
    public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {
        RealmSchema schema = realm.getSchema();
            
        ......
        
        // Modify your check according to your version update.
        if (oldVersion == 1) {
            // Below I am going to change the type of field 'id' from 'String' to 'int'

            // Get Schema of a Particular Class. Change --Testing-- with the respected pojo class name
            RealmObjectSchema schema = schema.get("Testing");

            // Add a new temporary field with the new type which you want to migrate. 'id_tmp' is a temporary integer field.
            schema.addField("id_tmp", int.class);

            // Set the previous value to the new temporary field
            schema.transform(new RealmObjectSchema.Function() {
                @Override
                public void apply(DynamicRealmObject obj) {
                    // Implement the functionality to change the type. Below I just transformed a string type to int type by casting the value. Implement your methodology below.
                    String id = obj.getString("id");

                    obj.setInt("id_tmp", Integer.valueOf(id));
                }
            });

            // Remove the existing field
            schema.removeField("id");

            // Rename the temporary field which hold the transformed value to the field name which you insisted to migrate.
            schema.renameField("id_tmp", "id");
            
            oldVersion++;
        }
        
        ......
        
    }
}

不要忘记更新架构版本并在RealmConfiguration领域实例中引用上述迁移类实例。