How to conditionally add a condition to my objectbox query?

I have this method to find all my Clientes:

static Future<List<Cliente>> findAll({
  int limit = 50,
  String? cnpjCpf,
  String? fantasia,
}) async {
  List<Cliente> clientes = [];

  final boxCliente = objectBox.store.box<Cliente>();

  Query<Cliente> query = boxCliente
      .query(Cliente_.cnpjCpf
          .contains(cnpjCpf ?? "")
          .or(Cliente_.fantasia.contains(fantasia ?? "")))
      .order(Cliente_.fantasia)
      .build();

  query.limit = limit;

  clientes = await query.findAsync();

  return clientes;
}

Now, instead of adding all conditions like the sample above, I need to conditionally add my conditions, i.e, if cnpjCpj != null then add it to the QueryBuilder.

I was thinking, maybe something like this:

static Future<List<Cliente>> findAll({
  int limit = 50,
  String? cnpjCpf,
  String? fantasia,
}) async {
  List<Cliente> clientes = [];

  final boxCliente = objectBox.store.box<Cliente>();

  final queryBuilder = boxCliente.query();

  if (cnpjCpf != null && cnpjCpf.isNotEmpty) {
    queryBuilder.equal(Cliente_.cnpjCpf, cnpjCpf);
  }

  if (fantasia != null && fantasia.isNotEmpty) {
    queryBuilder.contains(Cliente_.fantasia, fantasia);
  }

  queryBuilder.order(Cliente_.fantasia);

  Query<Cliente> query = queryBuilder.build();

  query.limit = limit;

  clientes = await query.findAsync();

  return clientes;
}

Any one knows how to do this? there is no equals or contains to the QueryBuilder object.

First combine the conditions, then once done pass them to the .query(conditions) method. So something like:

var Condition<Cliente>? conditions = null;

if (cnpjCpf != null && cnpjCpf.isNotEmpty) {
  conditions = Cliente_.cnpjCpf.equal(cnpjCpf);
}

if (fantasia != null && fantasia.isNotEmpty) {
  if (conditions == null) {
    conditions = Cliente_.fantasia.equal(fantasia);
  } else {
    conditions = conditions.or(Cliente_.fantasia.equal(fantasia));
  }
}

if (conditions != null) {
  final query = boxCliente.query(conditions).build();
}