Dependency Modules

By using Brandi, you can organize bindings in dependency modules. In this section we will see how to create, organize and use your modules.

DependencyModule is a logical space to help you organize your bindings. It is similar to Container, but it can only store dependencies, but not resolve or inject them.

DependencyModule Methods

DependencyModule repeats the following Container methods:

• bind(token)
• use(...tokens).from(module)
• when(condition)

Using Dependency Modules

Simple Example

Let's take an simple example, with using a binding from a module by the token:

import { Container, DependencyModule, token } from 'brandi';

const TOKENS = {

apiKey: token<string>('apiKey'),

};

const apiModule = new DependencyModule();

apiModule.bind(TOKENS.apiKey).toConstant('#key9428');

const container = new Container();

container.use(TOKENS.apiKey).from(apiModule);

const key = container.get(TOKENS.apiKey);

expect(key).toBe('#key9428');

Container will resolve the apiKey dependency from the module.

More Complex Example

In this example, we have the ApiService that depends on a apiKey, API dependency module, and the App that depends on an ApiService.

Let's start with the token declaration:

tokens.ts

import { token } from 'brandi';

import type { ApiService } from './api/ApiService';

import type { App } from './App';

export const TOKENS = {

apiKey: token<string>('apiKey'),

apiService: token<ApiService>('apiService'),

app: token<App>('app'),

};

Then we will create the ApiService with a dependency on a apiKey:

api/ApiService.ts

import { injected } from 'brandi';

import { TOKENS } from '../tokens';

export class ApiService {

constructor(private apiKey: string) {}

/* ... */

}

injected(ApiService, TOKENS.apiKey);

Then we will create the dependency module to which we will bind all the dependencies necessary for the API module:

api/module.ts

import { DependencyModule } from 'brandi';

import { TOKENS } from '../tokens';

import { ApiService } from './ApiService';

export const apiModule = new DependencyModule();

apiModule.bind(TOKENS.apiKey).toConstant('#key9428');

apiModule.bind(TOKENS.apiService).toInstance(ApiService).inTransientScope();

Creating our App that depends on ApiService:

App.ts

import { injected } from 'brandi';

import { TOKENS } from './tokens';

import type { ApiService } from './api/ApiService';

export class App {

constructor(private apiService: ApiService) {}

/* ... */

}

injected(App, TOKENS.apiService);

And finally configure the container:

container.ts

import { Container } from 'brandi';

import { TOKENS } from './tokens';

import { apiModule } from './api/module';

import { App } from './App';

export const container = new Container();

/**

* ↓ We only use the `apiService` token that the `App` directly depends on.

* The `apiKey` token binding will be resolved from the `apiModule` automatically

* and it does not need to be bound additionally.

*/

container.use(TOKENS.apiService).from(apiModule);

container.bind(TOKENS.app).toInstance(App).inSingletonScope();

Let's run:

index.ts

import { TOKENS } from './tokens';

import { container } from './container';

const app = container.get(TOKENS.app);

app.run();

note

Some of your dependency modules may use bindings from other modules. If there are bindings of the same token in the module chain, the highest-level binding in the hierarchy will be used.

createDependencyModule()

createDependencyModule() — is alias for new DependencyModule().