Method Init

cpp/src/arrow/json/from_string.cc:776–800

  explicit UnionConverter(const std::shared_ptr<DataType>& type) { type_ = type; }

  Status Init() override {
    auto union_type = checked_cast<const UnionType*>(type_.get());
    mode_ = union_type->mode();
    type_id_to_child_num_.clear();
    type_id_to_child_num_.resize(union_type->max_type_code() + 1, -1);
    int child_i = 0;
    for (auto type_id : union_type->type_codes()) {
      type_id_to_child_num_[type_id] = child_i++;
    }
    std::vector<std::shared_ptr<ArrayBuilder>> child_builders;
    for (const auto& field : type_->fields()) {
      std::shared_ptr<JSONConverter> child_converter;
      RETURN_NOT_OK(GetConverter(field->type(), &child_converter));
      child_converters_.push_back(child_converter);
      child_builders.push_back(child_converter->builder());
    }
    if (mode_ == UnionMode::DENSE) {
      builder_ = std::make_shared<DenseUnionBuilder>(default_memory_pool(),
                                                     std::move(child_builders), type_);
    } else {
      builder_ = std::make_shared<SparseUnionBuilder>(default_memory_pool(),
                                                      std::move(child_builders), type_);
    }
    return Status::OK();
  }

  // Append a JSON value that must be a 2-long array, containing the type_id
  // and value of the UnionArray's slot.