Trait TreeModel 

pub trait TreeModel {
    // Required methods
    fn root_id(&self) -> u64;
    fn contains(&self, id: u64) -> bool;
    fn label(&self, id: u64) -> Option<&str>;
    fn is_branch(&self, id: u64) -> bool;
    fn parent_id(&self, id: u64) -> Option<u64>;
    fn child_index(&self, parent: u64, child: u64) -> Option<usize>;
    fn child_count(&self, parent: u64) -> usize;
    fn child_id(&self, parent: u64, index: usize) -> Option<u64>;

    // Provided methods
    fn accepts_children(&self, id: u64) -> bool { ... }
    fn semantic_key(&self, _id: u64) -> Option<String> { ... }
    fn is_selectable(&self, _id: u64) -> bool { ... }
    fn is_renamable(&self, _id: u64) -> bool { ... }
    fn shows_row_actions(&self, _id: u64) -> bool { ... }
    fn can_collapse(&self, _id: u64) -> bool { ... }
    fn child_state(&self, parent: u64, index: usize) -> TreeChildState<'_> { ... }
    fn request_load(&mut self, _request: TreeLoadRequest) -> bool { ... }
    fn poll_changes(&mut self) -> Vec<TreeModelChange> { ... }
    fn needs_poll(&self) -> bool { ... }
}

Source-agnostic hierarchy queried by stable id. Implementations may be backed by a database, an async cache, a CRDT, or the owned TreeNode adapter. The view asks only for expanded children and visible labels. IDs must be unique, parent/child queries must be inverse, and the reachable hierarchy must be acyclic.

Required Methods

fn root_id(&self) -> u64

fn contains(&self, id: u64) -> bool

fn label(&self, id: u64) -> Option<&str>

fn is_branch(&self, id: u64) -> bool

fn parent_id(&self, id: u64) -> Option<u64>

Parent of id; None only for the root or an unknown id.

fn child_index(&self, parent: u64, child: u64) -> Option<usize>

Position of a direct child. Large/paged models should answer this from an index rather than scanning siblings.

fn child_count(&self, parent: u64) -> usize

fn child_id(&self, parent: u64, index: usize) -> Option<u64>

Provided Methods

fn accepts_children(&self, id: u64) -> bool

Whether a drop or an indent may make id a parent. Defaults to Self::is_branch; a hierarchy where any node can hold children (an outline, a notebook) answers true for leaves too, while Self::is_branch keeps deciding which rows show a disclosure.

fn semantic_key(&self, _id: u64) -> Option<String>

A durable identity for id in the semantic tree ("notes:page:<uuid>"), for models whose node ids are only stable within a session. Assistive technology and automation then address the row by it across launches.

fn is_selectable(&self, _id: u64) -> bool

Whether id can be chosen. A row that cannot (a section header in a navigation list) still takes focus and expands, but is never selected or activated.

fn is_renamable(&self, _id: u64) -> bool

Whether id’s label can be edited in place (see TreeView::on_rename).

fn shows_row_actions(&self, _id: u64) -> bool

Whether id’s row shows the tree’s row actions on hover and focus.

fn can_collapse(&self, _id: u64) -> bool

Whether an expanded branch may be collapsed. A heading whose rows are always shown answers false.

fn child_state(&self, parent: u64, index: usize) -> TreeChildState<'_>

Resolve a logical child slot. Paged models override this to return TreeChildState::Loading or TreeChildState::Error for non-resident rows; existing fully-resident models need only implement Self::child_id.

fn request_load(&mut self, _request: TreeLoadRequest) -> bool

Start or deduplicate work for one visible/retried child slot. Return whether the model accepted the request. Model-owned asynchronous sources can complete through Self::poll_changes; external owners may instead use TreeView::on_load_request.

fn poll_changes(&mut self) -> Vec<TreeModelChange>

Drain model-owned structural, row-data, or slot-state changes.

fn needs_poll(&self) -> bool

Keep scheduling frames only for sources that cannot wake the app when a batch completes. Prefer crate::LatestRequest for idle workers.

Implementors

impl<T> TreeModel for TreeNode<T>