mojo/public/tools/bindings/generators/cpp_templates/union_data_view_declaration.tmpl

class {{union.name}}DataView {
 public:
  using Tag = internal::{{union.name}}_Data::{{union.name}}_Tag;

  {{union.name}}DataView() {}

  {{union.name}}DataView(
      internal::{{union.name}}_Data* data,
      mojo::internal::SerializationContext* context)
{%- if union|requires_context_for_data_view %}
      : data_(data), context_(context) {}
{%- else %}
      : data_(data) {}
{%- endif %}

  bool is_null() const {
    // For inlined unions, |data_| is always non-null. In that case we need to
    // check |data_->is_null()|.
    return !data_ || data_->is_null();
  }

  Tag tag() const { return data_->tag; }

{%- for field in union.fields %}
{%-   set kind = field.kind %}
{%-   set name = field.name %}
  bool is_{{name}}() const { return data_->tag == Tag::{{name|upper}}; }

{%-   if kind|is_object_kind %}
  inline void Get{{name|under_to_camel}}DataView(
      {{kind|cpp_data_view_type}}* output);

  template <typename UserType>
  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) {
    DCHECK(is_{{name}}());
    return mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
        data_->data.f_{{name}}.Get(), output, context_);
  }

{%-   elif kind|is_enum_kind %}
  template <typename UserType>
  WARN_UNUSED_RESULT bool Read{{name|under_to_camel}}(UserType* output) const {
    DCHECK(is_{{name}}());
    return mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
        data_->data.f_{{name}}, output);
  }

  {{kind|cpp_data_view_type}} {{name}}() const {
    DCHECK(is_{{name}}());
    return static_cast<{{kind|cpp_data_view_type}}>(
        data_->data.f_{{name}});
  }

{%-   elif kind|is_any_handle_kind %}
  {{kind|cpp_data_view_type}} Take{{name|under_to_camel}}() {
    DCHECK(is_{{name}}());
    {{kind|cpp_data_view_type}} result;
    bool ret =
        mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
            &data_->data.f_{{name}}, &result, context_);
    DCHECK(ret);
    return result;
  }

{%-   elif kind|is_any_interface_kind %}
  template <typename UserType>
  UserType Take{{name|under_to_camel}}() {
    DCHECK(is_{{name}}());
    UserType result;
    bool ret =
        mojo::internal::Deserialize<{{kind|unmapped_type_for_serializer}}>(
            &data_->data.f_{{name}}, &result, context_);
    DCHECK(ret);
    return result;
  }

{%-   else %}
  {{kind|cpp_data_view_type}} {{name}}() const {
    DCHECK(is_{{name}}());
    return data_->data.f_{{name}};
  }

{%-   endif %}
{%- endfor %}

 private:
  internal::{{union.name}}_Data* data_ = nullptr;
{%- if union|requires_context_for_data_view %}
  mojo::internal::SerializationContext* context_ = nullptr;
{%- endif %}
};