Struct NestedChangeset 

pub struct NestedChangeset<P, C> {
    pub parent: Changeset<P>,
    /* private fields */
}

A parent Changeset<P> plus its bound child collection.

Obtain one from decode_nested_urlencoded or (preferred) the NestedChangesetForm axum extractor.

Fields

parent: Changeset<P>

The parent changeset (values + per-field errors), reusing the existing Changeset pipeline.

Implementations

impl<P, C: NestedChild> NestedChangeset<P, C>

pub fn blank(parent: P) -> Self

Build a blank, non-validating nested changeset for the initial new (create) render, before the user has submitted anything.

Mirrors ChangesetForm::blank: it wraps parent in a valid Changeset (via Changeset::new, which records no errors — it does not run validator::Validate) with zero child rows. So is_valid() returns true, errors_for(..) is empty, rows() is empty, and into_valid() returns Ok((parent, vec![])) even when a required parent field is still empty.

Use this for the initial GET render of an empty (create) form so the blank page does not show a premature “field is required” error or aria-invalid="true" before the user has typed. For an edit render that must display existing child rows (with their persisted ids), use seeded instead — blank produces zero child rows and cannot pre-fill or preserve existing line items. Use decode_nested_urlencoded (or the NestedChangesetForm extractor) for the POST decode that validates a real submission and re-renders with inline errors.

pub fn is_valid(&self) -> bool

true when the parent is valid, every non-destroyed row has no errors, and the children all parsed and validated.

pub fn into_valid(self) -> Result<(P, Vec<C>), Self>

Consume the changeset, returning Ok((parent, children)) when valid or Err(self) (with all rows retained for re-render) when not.

The returned child vector contains only non-destroyed rows, in order.

Errors

Returns Err(self) when the parent or any non-destroyed child row has validation errors, or any child failed to parse.

pub fn errors_for(&self, key: &str) -> &[String]

Validation messages for key, or an empty slice.

Supports both parent field keys (delegated to Changeset::errors_for) and combined child keys of the form "{COLLECTION}[{i}].{sub}" (e.g. "items[1].quantity"). A bare "{COLLECTION}[{i}]" returns that row’s row-level (parse) errors.

pub fn rows(&self) -> &[NestedRow]

The submitted child rows in compacted (ascending-index) order.

pub const fn collection_name(&self) -> &'static str

The child collection name, i.e. NestedChild::COLLECTION.

impl<P, C: NestedChild + Serialize> NestedChangeset<P, C>

Edit-render seeding — pre-populate a non-validating changeset with existing persisted children.

The extra serde::Serialize bound lives on this impl block alone, so the core NestedChild trait stays serialize-free; only callers that seed an edit form need their child type to be serializable.

pub fn seeded(parent: P, children: Vec<C>) -> Self

Build a non-validating, valid nested changeset that pre-renders one row per existing child, for the initial edit render of a form that already has persisted children.

Where blank produces zero child rows (for the create/new page), seeded produces exactly one NestedRow per element of children, so an edit form can display and preserve existing line items — including each child’s id as a hidden input (via RowScope::hidden_input) — before the first submit. That hidden id also makes the in-scope _destroy-on-existing-children flow usable: the row round-trips its identity so ticking Remove on a persisted child submits a real, identifiable row for the handler to delete.

Each row’s raw values are produced by serializing the child with serde_urlencoded::to_string and parsing the result back into the per-subfield map — the same string representation decode_nested_urlencoded populates from a real submission, so RowScope::value pre-fills a seeded row’s inputs identically to a re-rendered submitted row.

Like blank, this does not run validator::Validate: it wraps parent in a valid Changeset (via Changeset::new) and keeps valid_children = Some(children), so is_valid() returns true, errors_for(..) is empty, every seeded row reports no errors and is not destroyed, and into_valid() returns Ok((parent, children)). Use the POST decode path (decode_nested_urlencoded / the NestedChangesetForm extractor) to validate the actual edit submission.

Deeper reconciliation of persisted children — reordering, or deep-diffing submitted rows against the seeded set to compute per-row inserts / updates / deletes — is intentionally out of scope here (see issue #1346’s out-of-scope list) and remains a follow-up; seeded only pre-renders the existing rows so the no-JS edit + _destroy flow works.

Trait Implementations

impl<P: Debug, C: Debug> Debug for NestedChangeset<P, C>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.