TreeItem

TreeItem is the recursive data record used by TreeView.

Each item represents one node in a hierarchy. It can have its own label, optional icon, child items, and selection or expansion actions.

Example

use fission::prelude::*;

let item = TreeItem {
    id: "src".into(),
    icon: None,
    label: "src/".into(),
    children: vec![TreeItem {
        id: "main_rs".into(),
        icon: None,
        label: "main.rs".into(),
        children: vec![],
        on_toggle: None,
        on_select: Some(open_main_file_action),
    }],
    on_toggle: Some(toggle_src_folder_action),
    on_select: Some(select_src_folder_action),
};

Field table

Field	Type	Meaning	Notes / default behavior
id	String	Stable item identifier.	Required. Used by TreeView.expanded_ids and selected_id.
icon	Option<String>	Optional leading icon source.	Defaults to None.
label	String	Visible node label.	Required.
children	Vec<TreeItem>	Child widgets nested under this item.	Defaults to an empty list.
on_toggle	Option<ActionEnvelope>	Intended expansion-toggle action.	Present in the public struct, but see note below.
on_select	Option<ActionEnvelope>	Action fired when the row is selected.	Defaults to None.

Current implementation note

TreeItem exposes on_toggle, but the checked-in TreeView renderer does not currently render a separate expansion affordance or invoke that action for you. Expansion is still reflected through expanded_ids, but the interaction path must be composed carefully at the app level.

Production checklist

For TreeItem, review the fields that change behavior before treating the widget as finished: id, icon, label, children, on_toggle, on_select. The goal is to make the product rule visible in state and actions, not hidden inside ad-hoc construction code.

•

Bind on_toggle, on_select to explicit reducer actions and test that the reducer handles unavailable, duplicate, or invalid input safely.

•

When child widgets are generated from data, give reordered or filtered rows an explicit WidgetId so retained local state and scroll behavior do not drift between items.

•

Set id only when identity must be stable across filtering, reordering, diagnostics, or tests; otherwise let Fission derive identity from structure.

•

Check the semantics tree for the user-facing label or role that makes this widget understandable without relying only on pixels.

•

Add at least one component or harness test that confirms the visible text, semantic role, action dispatch, and layout constraint that matter for this widget in context.

If a screen starts repeating the same TreeItem setup, extract a named component around this widget. That keeps the reference API small while making product code easier to read and safer for generated code to copy.

TreeView, Breadcrumb, Icon, and Text.