Define components and agent templates

Define a component

A component is a plain type. Keep it Copy where you can — components are stored in columnar arrays and copied during migration.

#[derive(Clone, Copy, Default)]
struct Position {
    x: i64,
}

Register it and freeze the registry before building the model:

let registry = Arc::new(RwLock::new(ComponentRegistry::new()));
let position_id = registry.write().unwrap().register::<Position>()?;
registry.write().unwrap().freeze();

register returns the ComponentID you pass to templates and populations. Freeze once, after all component types are registered.

Define an agent template

Requires the agents feature (implied by model).

A template names a kind of agent and lists its components and capacity:

let walker = AgentTemplate::builder("walker")
    .with_component::<Position>(position_id)?
    .with_capacity(10_000)
    .build();

Register templates on the builder with with_agent_template. A template with several components lists each with_component before build; the population is then supplied one column per component (see initialise and mutate populations).

Multi-component agents

Give a template every component the agent kind has:

AgentTemplate::builder("firm")
    .with_component::<Firm>(ids.firm)?
    .with_component::<FirmStocks>(ids.firm_stocks)?
    .with_capacity(firm_count)
    .build()

The capacity should be the expected population so the columns are allocated once rather than grown incrementally.