98 lines
2.5 KiB
Markdown
98 lines
2.5 KiB
Markdown
# Node Nx Tutorial - Step 4: Create Libraries
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{% youtube
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src="https://www.youtube.com/embed/V29I_DHGlB8"
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title="Nx.dev Tutorial | Node | Step 4: Create Libraries"
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width="100%" /%}
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Libraries are not just a way to share code in Nx. They are also useful for factoring out code into small units with a well-defined public API.
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## Public API
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Every library has an `index.ts` file, which defines its public API. Other applications and libraries should only access what the `index.ts` exports. Everything else in the library is private.
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## Controller libraries
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To illustrate how useful libraries can be, create a new Auth library with a controller.
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Run
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```bash
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nx g @nrwl/nest:lib auth --controller
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```
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{% callout type="note" title="--controller" %}
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We added the `--controller` flag here to generate a controller along with the library scaffolding.
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{% /callout %}
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You should see the following:
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```treeview
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myorg/
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├── apps/
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│ └── todos/
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├── libs/
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│ ├── auth/
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│ │ ├── jest.config.ts
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│ │ ├── src/
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│ │ │ ├── index.ts
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│ │ │ └── lib/
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│ │ │ ├── auth.controller.spec.ts
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│ │ │ ├── auth.controller.ts
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│ │ │ └── auth.module.ts
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│ │ ├── tsconfig.json
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│ │ ├── tsconfig.lib.json
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│ │ └── tsconfig.spec.json
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│ └── data/
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├── tools/
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├── nx.json
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├── package.json
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└── tsconfig.base.json
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```
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Modify the `libs/auth/src/lib/auth.controller.ts` file like this:
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```typescript
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import { Controller, Get } from '@nestjs/common';
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@Controller('auth')
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export class AuthController {
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@Get()
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auth() {
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return {
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authenticated: true,
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};
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}
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}
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```
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{% callout type="note" title="We keep things simple here" %}
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In code destined for production, you would actually have a proper authentication check here.
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{% /callout %}
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## Use the new library
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**Now import `AuthModule` into `apps/todos/src/app/app.module.ts`.**
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```typescript
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import { Module } from '@nestjs/common';
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import { AppController } from './app.controller';
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import { AppService } from './app.service';
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import { TodosService } from './todos/todos.service';
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import { AuthModule } from '@myorg/auth';
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@Module({
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imports: [AuthModule],
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controllers: [AppController],
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providers: [AppService, TodosService],
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})
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export class AppModule {}
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```
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Restart `nx serve todos` then go to http://localhost:3333/auth. You should see `{ authenticated: true }`.
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## What's Next
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- Continue to [Step 5: Dep graph](/node-tutorial/05-dep-graph)
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