@dolittle/sdk.projections/Distribution/IProjection.d.ts

Dolittle is a decentralized, distributed, event-driven microservice platform built to harness the power of events.

import { Constructor } from '@dolittle/types';
import { EventType, ScopeId } from '@dolittle/sdk.events';
import { ProjectionCopies } from './Copies/ProjectionCopies';
import { DeleteReadModelInstance } from './DeleteReadModelInstance';
import { EventSelector } from './EventSelector';
import { ProjectionContext } from './ProjectionContext';
import { ProjectionAlias } from './ProjectionAlias';
import { ProjectionId } from './ProjectionId';
/**
 * Defines a projection.
 * @template T The type of the projection read model.
 */
export declare abstract class IProjection<T> {
    /**
     * Gets the {@link ProjectionId} for the projection.
     */
    abstract readonly projectionId: ProjectionId;
    /**
     * Gets the class of read model type if created from a class.
     */
    abstract readonly readModelType: Constructor<T> | undefined;
    /**
     * Gets the initial state of the projection.
     */
    abstract readonly initialState: T;
    /**
     * Gets the scope the projection is in.
     */
    abstract readonly scopeId: ScopeId;
    /**
     * Gets the events used by the projection.
     */
    abstract readonly events: Iterable<EventSelector>;
    /**
     * Gets the specification of read model copies to produce for the projection.
     */
    abstract readonly copies: ProjectionCopies;
    /**
     * Gets the alias for the projection.
     */
    abstract readonly alias: ProjectionAlias | undefined;
    /**
     * Gets a value indicating whether this projection has an alias or not.
     */
    abstract readonly hasAlias: boolean;
    /**
     * Handle an event and update a readmodel.
     * @param {T} readModel - ReadModel to update.
     * @param {*} event - Event to handle.
     * @param {EventType} eventType - The event type.
     * @param {ProjectionContext} context - The context for the projection processing.
     */
    abstract on(readModel: T, event: any, eventType: EventType, context: ProjectionContext): Promise<T | DeleteReadModelInstance> | T | DeleteReadModelInstance;
}
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