@almin/usecase-bus

A mediator for UseCase and Command. This library provide Command Bus.

What is Command and Command handler pattern?

• Implementing the microservice application layer using the Web API | Microsoft Docs
  • 日本語訳

Command

• A bus send Command to a single Command Handler
• Command may be rejected by system
• Command may be failed during executing in Handler
• Command may be various effect in system state
• Command does not be over the boundary
• Command should have imperative named.

What is merits?

• Flexible
• Retry the UseCase
• Logging
• Adoptable
• Additional Event

What is de-merits?

• Add new Layer(CommandBus)

Install

Install with npm:

npm install @almin/usecase-bus

Usage

import { UseCase, Context } from "almin";
import { UseCaseCommandBus } from "@almin/usecase-bus"
// async code
(async () => {
    const context = new Context({
        store: new NopeStore()
    });

    class CommandA {
        type = "CommandA";
    }

    class CommandB {
        type = "CommandB";
    }

    const executed: (CommandA | CommandB)[] = [];

    class TestUseCaseA extends UseCase {
        execute(command: CommandA) {
            executed.push(command);
        }
    }

    class TestUseCaseB extends UseCase {
        execute(command: CommandB) {
            executed.push(command);
        }
    }

    const createTestUseCaseB = (_command: CommandB) => {
        return new TestUseCaseB();
    };

    // create binding between Command Constructor and UseCase/UseCaseFactory.
    const bus = UseCaseCommandBus.create(context)
        .bind(CommandA, new TestUseCaseA())
        .bindFactory(CommandB, createTestUseCaseB);
    // send CommandA => execute TestUseCaseA
    await bus.send(new CommandA());
    assert.strictEqual(executed.length, 1);
    assert.ok(executed[0] instanceof CommandA);
    // send CommandB => execute createTestUseCaseB()
    await bus.send(new CommandB());
    assert.strictEqual(executed.length, 2);
    assert.ok(executed[1] instanceof CommandB);
})()

Changelog

See Releases page.

Reference

• Implementing the microservice application layer using the Web API | Microsoft Docs
  • 日本語訳
• predaddy/src/predaddy/messagehandling at 3.0 · szjani/predaddy
• jbogard/MediatR: Simple, unambitious mediator implementation in .NET

Contributing

Pull requests and stars are always welcome.

For bugs and feature requests, please create an issue.

1. Fork it!
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes: git commit -am 'Add some feature'
4. Push to the branch: git push origin my-new-feature
5. Submit a pull request :D

Author

• github/azu
• twitter/azu_re

License

MIT © azu