Module zng::state_map

Hash-map of type erased values, useful for storing assorted dynamic state.

A new map can be instantiated using OwnedStateMap, but in a typical app you use maps provided by the API. The most common widget maps are WIDGET.with_state_mut that is associated with the widget instance and WidgetInfoBuilder::with_meta that is associated with the widget info.

use zng::{prelude::*, prelude_wgt::*};

static_id! {
    static ref STATE_ID: StateId<bool>;
}

/// Extends [`WidgetInfo`] with state.
pub trait StateWidgetInfoExt {
    /// Gets the state.
    fn state(&self) -> Option<bool>;
}
impl StateWidgetInfoExt for WidgetInfo {
    fn state(&self) -> Option<bool> {
        self.meta().get_clone(*STATE_ID)
    }
}

/// State the state info.
#[property(CONTEXT)]
pub fn state(child: impl UiNode, state: impl IntoVar<bool>) -> impl UiNode {
    let state = state.into_var();
    match_node(child, move |_, op| match op {
        UiNodeOp::Init => {
            WIDGET.sub_var_info(&state);
        }
        UiNodeOp::Info { info } => {
            info.set_meta(*STATE_ID, state.get());
        }
        _ => {}
    })
}

Full API

See zng_state_map for the full API.

Structs

• OccupiedStateMapEntry
  A view into an occupied entry in a state map.
• OwnedStateMap
  Private state map.
• StateId
  Unique identifier of a value in a state map.
• StateMapMut
  Mutable state map.
• StateMapRef
  Read-only state map.
• VacantStateMapEntry
  A view into a vacant entry in a state map.

Enums

• StateMapEntry
  A view into a single entry in a state map, which may either be vacant or occupied.

Traits

• StateValue
  Represents a type that can be a StateId value.