Migrate realm field of type double to new sub-object with values

Question

I have a User object right now that has a bunch of values in it, saved as doubles. The format of our api json is now changing to include two values for each field. So I have created a Value object (which extends RealmObject) and it contains the two values.

So now in my user object I want to do the following

//Current way
private Double balance;

//Want to migrate to this
private Value balance;

The Value object looks like this:

private class Value extends RealmObject {

    private Integer value;
    private String formattedValue;

    //getters/setters
}

My question is, how can I express this change in a RealmMigration?

This is what I have so far based on this: (Change datatype of Realm field - Java)

schema.get("User")
            .addField("balance_tmp", Value.class)
            .transform(new RealmObjectSchema.Function() {
                @Override
                public void apply(DynamicRealmObject obj) {
                    //what goes here? how can I access the Value.class and call setValue()?
                }
            })
            .removeField("balance")
            .renameField("balance_tmp", "balance");

Is this even possible? Or should I be resigned to fact that any data assigned to the fields I change will be lost?

Answer 1

Something like this should work:

RealmObjectSchema valueSchema = schema.create("Value")
        .addField("value", Integer.class)
        .addField("formattedValue", String.class);

schema.get("User")
        .addRealmObjectField("balance_tmp", valueSchema)
        .transform(new RealmObjectSchema.Function() {
            @Override
            public void apply(DynamicRealmObject obj) {
                int balance = obj.getInt("balance");
                DynamicRealmObject valueObj = obj.getObject("balance_tmp");
                valueObj.setInt("value", balance);
                valueObj.setString("formattedValue", format(balance));
            }
        })
        .removeField("balance")
        .renameField("balance_tmp", "balance");