164 lines
4.2 KiB
Markdown
164 lines
4.2 KiB
Markdown
# Step 8: Create Libs
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## Video of this Lesson
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<iframe width="560" height="315" src="https://www.youtube.com/embed/szaH7fNw0zg" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
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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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## UI Libraries
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To illustrate how useful libraries can be, create a library of Angular components.
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**Run `nx g @nrwl/angular:lib ui`.**
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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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│ ├── todos-e2e/
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│ └── api/
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├── libs/
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│ ├── data/
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│ └── ui/
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│ ├── src/
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│ │ ├── lib/
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│ │ │ ├── ui.module.spec.ts
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│ │ │ └── ui.module.ts
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│ │ └── index.ts
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│ ├── jest.conf.js
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│ ├── tsconfig.app.json
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│ ├── tsconfig.json
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│ ├── tsconfig.spec.json
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│ └── tslint.json
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├── nx.json
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├── package.json
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├── tools/
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├── tsconfig.json
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└── tslint.json
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```
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The `libs/ui/src/lib/ui.module.ts` file looks like this:
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```typescript
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import { NgModule } from '@angular/core';
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import { CommonModule } from '@angular/common';
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@NgModule({
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imports: [CommonModule],
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})
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export class UiModule {}
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```
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## Add a Component
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**Add a component to the newly created ui library by running:**
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```bash
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nx g component todos --project=ui --export
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```
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```treeview
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myorg/
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├── apps/
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│ ├── todos/
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│ ├── todos-e2e/
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│ └── api/
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├── libs/
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│ ├── data/
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│ └── ui/
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│ ├── src/
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│ │ ├── lib/
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│ │ │ ├── todos/
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│ │ │ │ ├── todos.component.css
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│ │ │ │ ├── todos.component.html
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│ │ │ │ ├── todos.component.spec.ts
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│ │ │ │ └── todos.component.ts
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│ │ │ ├── ui.module.spec.ts
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│ │ │ └── ui.module.ts
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│ │ └── index.ts
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│ ├── jest.conf.js
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│ ├── tsconfig.app.json
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│ ├── tsconfig.json
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│ ├── tsconfig.spec.json
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│ └── tslint.json
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├── nx.json
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├── package.json
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├── tools/
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├── tsconfig.json
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└── tslint.json
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```
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**Add a `todos` input to `libs/ui/src/lib/todos/todos.component.ts`.**
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```typescript
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import { Component, OnInit, Input } from '@angular/core';
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import { Todo } from '@myorg/data';
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@Component({
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selector: 'myorg-todos',
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templateUrl: './todos.component.html',
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styleUrls: ['./todos.component.css'],
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})
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export class TodosComponent implements OnInit {
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@Input() todos: Todo[];
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constructor() {}
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ngOnInit() {}
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}
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```
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**And update `todos.component.html` to display the given todos:**
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```html
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<ul>
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<li *ngFor="let t of todos" class="todo">{{ t.title }}</li>
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</ul>
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```
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## Use the UI Library
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**Now import `UiModule` into `apps/todos/src/app/app.module.ts`.**
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```typescript
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import { BrowserModule } from '@angular/platform-browser';
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import { NgModule } from '@angular/core';
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import { AppComponent } from './app.component';
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import { HttpClientModule } from '@angular/common/http';
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import { UiModule } from '@myorg/ui';
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@NgModule({
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declarations: [AppComponent],
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imports: [BrowserModule, HttpClientModule, UiModule],
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providers: [],
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bootstrap: [AppComponent],
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})
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export class AppModule {}
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```
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**And update `app.component.html`:**
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```html
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<h1>Todos</h1>
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<myorg-todos [todos]="todos"></myorg-todos>
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<button (click)="addTodo()">Add Todo</button>
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```
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**Restart both `nx serve api` and `nx serve todos` and you should see the application running.**
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!!!!!
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Libraries' public API is defined in...
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!!!!!
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index.ts
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angular.json and tsconfig.json files
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