Trait CrowdObserver 

pub trait CrowdObserver {
    // Required method
    fn observe(&mut self, agent_id: AgentId, ped: &Pedestrian);
}

Per-agent post-step observation hook.

Invoked by step_scratch_store_observed after the model has finished the tick and the updated state has been written back to the store, so ped reflects the post-tick position, velocity, and destination. Closes the P1 “telemetry hooks” item from docs/rustsim-crowd.md: downstream code can forward each row into the workspace’s TelemetryPipeline::push_row, write it to a CSV logger, update a live heatmap, or compute rolling flow-density statistics — without rustsim-crowd itself taking a dependency on any sink implementation.

The trait is blanket-implemented for every FnMut(AgentId, &Pedestrian), so in practice callers pass a closure:

step_scratch_store_observed(
    &SocialForceModel, &mut store, &walls, &params, dt,
    &mut scratch, &mut peds_buf,
    |id, ped| pipeline.push_row(&[tick.into(), id.into(),
        ped.pos[0].into(), ped.pos[1].into(),
        ped.vel[0].into(), ped.vel[1].into()])?,
);

Implementations must not panic on valid inputs; the observer is called inside the tick loop and a panic aborts the whole tick.

Required Methods

fn observe(&mut self, agent_id: AgentId, ped: &Pedestrian)

Observe the post-tick state of one pedestrian.

Implementors

impl<F> CrowdObserver for F

where F: FnMut(AgentId, &Pedestrian),