nx/docs/angular/tutorial/07-share-code.md

Angular Nx Tutorial - Step 7: Share Code

Awesome! The application is working end to end! However, there is a problem. Both the backend and the frontend define the Todo interface. The interface is in sync now, but in a real application, over time, it will diverge, and, as a result, runtime errors will creep in. You should share this interface between the backend and the frontend. In Nx, you can do this by creating a library.

Run the following generator to create a library:

npx nx g @nrwl/workspace:lib data

The result should look like this:

myorg/
├── apps/
│   ├── todos/
│   ├── todos-e2e/
│   └── api/
├── libs/
│   └── data/
│       ├── src/
│       │   ├── lib/
│       │   │   └── data.ts
│       │   └── index.ts
│       ├── jest.conf.js
│       ├── tsconfig.app.json
│       ├── tsconfig.json
│       ├── tsconfig.spec.json
│       └── tslint.json
├── workspace.json
├── nx.json
├── package.json
├── tools/
├── tsconfig.base.json
└── tslint.json

Copy the interface into libs/data/src/lib/data.ts.

export interface Todo {
  title: string;
}

A note about VS Code :

If you're using VS Code it may be necessary at this point to restart the TS server so that the new @myorg/data package is recognized. This may need to be done every time a new workspace library is added.

Refactor the API

Now update apps/api/src/app/app.service.ts to import the interface:

import { Injectable } from '@nestjs/common';
import { Todo } from '@myorg/data';

@Injectable()
export class AppService {
  todos: Todo[] = [{ title: 'Todo 1' }, { title: 'Todo 2' }];

  getData(): Todo[] {
    return this.todos;
  }

  addTodo() {
    this.todos.push({
      title: `New todo ${Math.floor(Math.random() * 1000)}`,
    });
  }
}

Update the Angular application

Next import the interface in apps/todos/src/app/app.component.ts:

import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Todo } from '@myorg/data';

@Component({
  selector: 'myorg-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
})
export class AppComponent {
  todos: Todo[] = [];

  constructor(private http: HttpClient) {
    this.fetch();
  }

  fetch() {
    this.http.get<Todo[]>('/api/todos').subscribe((t) => (this.todos = t));
  }

  addTodo() {
    this.http.post('/api/addTodo', {}).subscribe(() => {
      this.fetch();
    });
  }
}

Every time you add a new library, you have to restart npx nx serve. So restart both npx nx serve api and npx nx serve todos and you should see the application running.