Rustango docs
← Cookbook

Chapter 7 — Forms + serializer

6 tests covering ModelFormFor<T> parse/from_json/error aggregation/ bound-validation/null handling/insert-query emission. No DB needed. Run with cargo test --test cookbook_chapter07_forms.

  • §7.95 ModelFormFor::<T>::parse(&HashMap<String,String>) — form- encoded payload → (columns, values) with per-field bound validation. Auto PK and auto_now_add columns are skipped (DB fills them). → modelform_parses_form_encoded_into_typed_values
  • §7.95 missing required fields aggregate into FormErrors, one entry per field. → modelform_missing_required_fields_aggregate_errors
  • §7.96 ModelFormFor::<T>::from_json(&serde_json::Value) — JSON request body. Null values on Option<T> write explicit SqlValue::Null. → modelform_from_json_parses_object, modelform_from_json_null_writes_explicit_null
  • §7.98 min/max bounds run at parse time. Out-of-range values land in FormErrors keyed by field. → modelform_bound_violation_lands_in_form_errors
  • §7.99 into_insert_query() emits an InsertQuery against the model's table. → modelform_into_insert_query_targets_model_table

Framework bug fixed during this slice: ModelFormFor::parse required EVERY field including auto_now_add columns (e.g. joined_at: Auto<DateTime<Utc>>), which the macro skips on INSERT because DEFAULT NOW() fills them. Fix: skip every auto = true field (was: only auto && primary_key).

7.99b #[derive(Serializer)] — DRF-shape JSON façade

6 tests in tests/cookbook_chapter07b_serializer.rs exercise the serializer derive against the cookbook's Author model. Run with cargo test --test cookbook_chapter07b_serializer.

  • from_model + to_value round-trip — every field maps from the model and lands in the JSON output. → serializer_from_model_then_to_value_round_trip
  • #[serializer(read_only)] — excluded from writable_fields(), still appears in JSON output. → read_only_field_omitted_from_writable_fields
  • #[serializer(write_only)] — excluded from JSON output, accepted on input. → write_only_field_excluded_from_json_output
  • #[serializer(source = "x")] — renames the JSON key to a different model field. → source_attribute_renames_json_key
  • #[serializer(skip)] — uses Default::default(), leaves the field in JSON but excludes it from writable_fields(). → skip_field_uses_default_and_appears_in_json_unchanged
  • many_to_value — batches a Vec<Model> into a JSON array. → many_to_value_batches_into_json_array

Framework fix during this slice: Auto<T> was missing an OpenApiSchema impl, so #[derive(Serializer)] failed to build with the openapi feature on for any model with Auto<T> fields. Added impl<T: OpenApiSchema> OpenApiSchema for Auto<T> (forwards to T's schema).

Gaps tracked in v0.18 DRF parity roadmap:

  1. Auto-nested FK — #[serializer(nested = AuthorSerializer)] that lazy-loads + nests the parent. Today: manual.
  2. SerializerMethodField — #[serializer(method = "fn_name")] computed fields. Today: manual after from_model.
  3. ViewSet ↔ Serializer wiring — ViewSet::for_model(...).serializer::<T>(). Today: ViewSet serializes the bare model.
  4. M2M many-relations — #[serializer(many = TagSerializer, source = "tags")]. Today: no automatic M2M traversal in serializers.
  5. Per-field validators chain — #[serializer(validate = "fn_name")] per-field validator callable. Today: only model-level min/max/max_length.

Sub-sections 7.93 (raw Form derive), 7.94 (admin's hand-rolled ModelForm engine), 7.97 (parse_form_value per type), 7.98b (custom validators) queued for Slice 7c.

← Cookbook