es cqrs.TypeAlias.Command

@sclable/nestjs-libs / es-cqrs / Command

Type Alias: Command

Command: INestCommand

Command interface

Implement this to create unique commands. There is no restriction on what the command class can have.

Example:

import { Command } from '@sclable/es-cqrs'
import { v4 } from 'uuid'

export class CreateAccountCommand implements Command {}

export class AccountNameChangeCommand implements Command {
  public constructor(public readonly id: string, public readonly name: string) {}
}

To handle these commands implement the ICommandHandler interface so that it finds or creates the needed aggregate, call the modifying method that will create the event and persist the aggregate in the repository. The resolve method should return the object needed for this command to finish (usually an ID).

Example:

import { CommandHandler, ICommandHandler, InjectRepository, Repository } from '@sclable/es-cqrs'
import { AccountNameChangeCommand } from './commands'
import { AccountAggregate } from './aggregates'

@CommandHandler(AccountNameChangeCommand)
export class SomeCommandHandler implements ICommandHandler<AccountNameChangeCommand> {

  public constructor(@InjectRepository(AccountAggregate) private readonly repo: Repository<AccountAggregate>) {}

  async execute(command: AccountNameChangeCommand): Promise<any> {
    const agg = await this.repo.find(command.id)
    agg.changeName(command.name)
    return this.repo.persist(agg)
  }
}

Defined in

packages/es-cqrs/src/interfaces/command.ts:43