Components play an important part in the extensibility of LoopBack 4. A Component makes it easy for independent developers to contribute additional features to LoopBack. Components serve as a vehicle to group extension contributions such as Context Bindings and various artifacts to allow easier extensibility of your Application.
A typical LoopBack component is an npm package exporting a Component class which can be added to your application.
import {RestApplication} from '@loopback/rest';
import {AuthenticationComponent} from '@loopback/authentication';
const app = new RestApplication();
// Add component to Application, which provides bindings used to resolve
// authenticated requests in a Sequence.
app.component(AuthenticationComponent);
Components can contribute the following items:
- Controllers
- Providers of additional Context values
LoopBack 4 was built with extensibility in mind and this includes Components,
which can be allowed to contribute additional artifacts by adding a Mixin to
your Application class. This doesn’t change how a Component is registered
(app.component()) but it enables the Component to contribute additional
artifacts. For example:
- Repositories can be contributed by a Component by adding
RepositoryMixinfrom@loopback/repositoryto your Application - Booters can be contributed by a Component
by adding
BootMixinfrom@loopback/bootto your Application
Note: Always check a component’s instructions to see if it requires the use of a Mixin. A Mixin may automatically register a Component, saving you the trouble of having to do so manually. Again it’s best to check the documentation for the given Component / Mixin.