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Standalone Components Angular:14

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Angular 14 introduces a groundbreaking feature called standalone components, which revolutionizes the way Angular applications are created and structured. With standalone components, you can now build an entire application without the need for custom Angular modules, simplifying the development process and providing greater flexibility.

So, what exactly is a standalone component?

A standalone component is a type of Angular component that is not associated with any specific Angular module. In previous versions of Angular, when creating a component, you had to include it in the declarations array of a module; otherwise, Angular would throw an error during compilation. However, starting from Angular 14, you can create components that exist independently without being part of any ngModule, and these components are referred to as standalone components.

In addition to standalone components, Angular 14 also introduces standalone directives and standalone pipes, expanding the scope of this new feature. This means you can create independent directives and pipes that are not tied to any specific module, providing more modularity and reusability in your Angular applications.

In addition to standalone components, Angular 14 also supports standalone directives and pipes. These standalone entities offer streamlined ways to develop Angular applications.

To create a standalone component, pipe, or directive, you can utilize the --standalone flag in the ng generate component command. For example:

ng g p search --standalone
ng g d credit-card --standalone
ng g c login --standalone

A standalone pipe looks like the below:

import { Pipe, PipeTransform } from "@angular/core";

@Pipe({
  name: "search",
  standalone: true,
})
export class SearchPipe implements PipeTransform {
  transform(value: unknown, ...args: unknown[]): unknown {
    return null;
  }
}

Standalone components can be used in various scenarios, including:

Module-based components: You can use standalone components within Angular modules by importing them and including them in the imports array of the module. This allows you to seamlessly integrate standalone components with existing module-based components.

Other standalone components: Standalone components can also be used with other standalone components. By importing and including them in the imports array of a standalone component, you can create modular and self-contained components that encapsulate specific functionality.

Loading routes: Standalone components can be used when defining routes in your Angular application. By configuring routes to load standalone components, you can dynamically load different components based on the route, enhancing the flexibility and performance of your application.

Upon executing the aforementioned command, the application will be updated with a newly added Login Component. It is worth noting that the standalone property of the component decorator is set to true. This signifies that the Login Component is a standalone component, independent of any Angular module.

import { Component, OnInit } from "@angular/core";
import { CommonModule } from "@angular/common";

@Component({
  selector: "app-login",
  standalone: true,
  imports: [CommonModule],
  templateUrl: "./login.component.html",
  styleUrls: ["./login.component.css"],
})
export class LoginComponent implements OnInit {
  constructor() {}

  ngOnInit(): void {}
}

If you mistakenly attempt to include a standalone component, directive, or pipe within an Angular module, Angular will raise an error indicating that it cannot be declared within an NgModule. The error message would resemble the following:

“Error: Component LoginComponent is standalone and cannot be declared in an NgModule. Did you mean to import it instead?”

This error serves as a reminder that standalone components should not be added to an NgModule, but rather imported and utilized as needed.

To convert an existing module-based component into a standalone component, you can follow these three essential points:

  1. Set the standalone property to true: In the component decorator, ensure that the standalone property is set to true. This indicates that the component is now a standalone component.
  2. Remove it from the declaration array of the module: Remove the component from the declaration array of the module it was previously part of. This step ensures that the component is no longer associated with any specific module.
  3. Use the imports array to add dependencies: If the standalone component relies on any dependencies, such as other components, directives, or pipes, you can include them in the imports array of the component decorator. This ensures that the necessary dependencies are available for the standalone component to function properly.

By following these three points, you can successfully convert a module-based component into a standalone component and leverage its standalone capabilities.

Managing Dependencies in Standalone Components

Handling Dependencies in Standalone Components

A standalone component often requires dependencies on other members, pipes, and directives, which can be categorized into two types:

  1. Standalone Dependencies: These are dependencies that are standalone components, directives, or pipes that are not part of any Angular module.
  2. Module Dependencies: These are dependencies that are part of an Angular module and need to be included in the standalone component.

Both types of dependencies can be added to a standalone component using the imports array of the @Component decorator. For instance, if the LoginComponent requires the ReactiveFormsModule dependency, you can add it to the imports array as shown in the code snippet below:

import { Component } from "@angular/core";
import { ReactiveFormsModule } from "@angular/forms";

@Component({
  selector: "app-login",
  imports: [ReactiveFormsModule],
  // ...
})
export class LoginComponent {
  // ...
}

By including the ReactiveFormsModule in the imports array, the LoginComponent can access and utilize the functionalities provided by the ReactiveFormsModule.

Remember, when working with standalone components, it is crucial to manage and include all the necessary dependencies in the imports array to ensure the component functions as intended.

Utilizing(Use Of) a Standalone Component

A standalone component can be utilized in different ways within an Angular application:

  1. Inside another standalone component: You can include a standalone component inside another standalone component by adding it to the imports array of the parent component. This allows you to compose your application using reusable standalone components.

Example:

import { Component } from "@angular/core";
import { LoginComponent } from "./login/login.component";

@Component({
  selector: "app-product",
  imports: [LoginComponent],
  // ...
})
export class ProductComponent {
  // ...
}
  1. Inside a module: If you want to use a standalone component within a module, you need to add it to the imports array of the module. However, standalone components should not be included in the declarations array of the module.

Example:

import { NgModule } from "@angular/core";
import { BrowserModule } from "@angular/platform-browser";
import { AppComponent } from "./app.component";
import { LoginComponent } from "./login/login.component";

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, LoginComponent],
  // ...
})
export class AppModule {
  // ...
}

By adding the LoginComponent to the imports array of the AppModule, you can use it within the templates of components declared in that module.

Remember to only include standalone components in the imports array and not in the declarations array when using them in a module.

Using standalone components allows for modular and reusable code, promoting component composition and separation of concerns within your Angular application.

Bootstrapping a Standalone Component

In Angular, you can bootstrap an application using a standalone component. Bootstrapping refers to the process of launching the application by initializing the root component.

To bootstrap a standalone component, follow these steps:

  1. Import the necessary dependencies: In the main.ts file, import the required dependencies for bootstrapping the application. This typically includes the bootstrapApplication function and the standalone component you want to bootstrap.
import { bootstrapApplication } from "@angular/platform-browser";
import { ProductComponent } from "./app/product/product.component";
  1. Call the bootstrapApplication function: Invoke the bootstrapApplication function and pass the standalone component as well as any required configuration options.
bootstrapApplication(ProductComponent, {
  providers: [],
});

The bootstrapApplication function is responsible for initializing the Angular application using the provided standalone component. You can also pass additional configuration options in the second parameter, such as providers for dependency injection.

  1. Update the index.html file: In the index.html file, replace the placeholder element (e.g., <app-root>) with the selector of the standalone component you're bootstrapping.
<body>
  <app-product></app-product>
</body>

By replacing the <app-root> element with <app-product>, the application will now be bootstrapped using the ProductComponent as the root component.

  1. Run the application: Start the Angular development server to run the application. The standalone component specified in the bootstrapApplication function will be loaded, and the application will be initialized from there.

Bootstrapping a standalone component allows you to define a specific entry point for your application, making it easier to integrate and control the initialization process.

Routing with Standalone Component

In Angular, you can implement routing with a standalone component to navigate between different views or pages within your application. The Angular Router module provides the necessary functionality for setting up and managing routing.

To implement routing with a standalone component, follow these steps:

  1. Set up the routes: Define the routes for your application in a separate routing module. This module will contain an array of route configurations, where each route specifies a path and the corresponding component to be rendered.
import { Routes } from "@angular/router";
import { HomeComponent } from "./home.component";
import { AboutComponent } from "./about.component";

export const routes: Routes = [
  { path: "", component: HomeComponent },
  { path: "about", component: AboutComponent },
];

In this example, we have two routes: the root route (‘’) maps to the HomeComponent, and the ‘about’ route maps to the AboutComponent.

2.Configure the router: In the app module or the module where your standalone component resides, import the RouterModule and call the forRoot method to configure the router with the defined routes.

import { RouterModule } from  '@angular/router';
import { routes } from  './app.routes';

@NgModule({
imports: [
RouterModule.forRoot(routes)
],
...
})
export class  AppModule { }

This configures the router with the provided routes and prepares it for navigation.

  1. Define the router outlet: In the template of your standalone component, add a <router-outlet></router-outlet> element. This acts as a placeholder where the content of the routed components will be rendered.
<div>
  <router-outlet></router-outlet>
</div>
  1. Set up navigation links: In your standalone component’s template or navigation menu, add links that correspond to the defined routes. Use the routerLink directive to navigate to the specified route when the link is clicked.
<nav>
  <a routerLink="/">Home</a>
  <a routerLink="/about">About</a>
</nav>

Clicking on these links will trigger the routing mechanism and load the corresponding components into the router outlet.

  1. Run the application: Start the Angular development server to run the application. You can now navigate between different views by clicking on the defined links, and the router will render the corresponding components in the router outlet of the standalone component.

Routing with a standalone component allows you to create a modular and navigable application structure, enabling users to switch between different views seamlessly.

On running the application, you should navigate the home route and get HomeComponent loaded.

Lazy Loading a Standalone Component

Lazy loading is a technique in Angular that allows you to load modules and components only when they are needed, improving the initial loading time of your application. Here’s how you can implement lazy loading for a standalone component:

  1. Create a separate module for the standalone component: Create a module specifically for the standalone component that you want to lazy load. This module will contain the component and any necessary dependencies.
import { NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";
import { RouterModule } from "@angular/router";
import { StandaloneComponent } from "./standalone.component";

@NgModule({
  declarations: [StandaloneComponent],
  imports: [CommonModule, RouterModule],
  exports: [StandaloneComponent],
})
export class StandaloneModule {}
  1. Configure the routing module for lazy loading: In the routing module of your application (e.g., AppRoutingModule), define a route that uses the loadChildren property to specify the path to the standalone module.
import { NgModule } from "@angular/core";
import { RouterModule, Routes } from "@angular/router";

const routes: Routes = [
  {
    path: "standalone",
    loadChildren: () =>
      import("./path/to/standalone.module").then((m) => m.StandaloneModule),
  },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule],
})
export class AppRoutingModule {}

In this example, the ‘standalone’ route is configured to lazy load the StandaloneModule. The loadChildren property uses dynamic import syntax to load the module only when the route is accessed.

  1. Update the navigation links: In your application’s navigation links, update the routerLink directive to point to the lazy-loaded route.
<a routerLink="/standalone">Standalone</a>

Clicking on this link will trigger the lazy loading mechanism, and the StandaloneModule will be loaded asynchronously.

  1. Run the application: Start your Angular development server, and when you navigate to the ‘standalone’ route, the StandaloneComponent will be loaded and displayed.

Lazy loading standalone components allows you to optimize the performance of your application by loading components on-demand. This is particularly useful when dealing with large applications with many features and modules, as it reduces the initial bundle size and improves the overall user experience.

Dependency Injection

Dependency Injection (DI) is a key feature in Angular that allows you to efficiently manage the dependencies of your components, services, and other objects. Here’s how you can configure DI for a standalone component:

  1. Define the dependencies: Identify the dependencies that your standalone component requires. These can be services, other components, or any other objects that need to be injected.
import { Component, OnInit } from "@angular/core";
import { DataService } from "../services/data.service";

@Component({
  selector: "app-standalone",
  templateUrl: "./standalone.component.html",
  styleUrls: ["./standalone.component.css"],
})
export class StandaloneComponent implements OnInit {
  constructor(private dataService: DataService) {}

  ngOnInit(): void {
    // Use the data service
    this.dataService.getData();
  }
}

In this example, the StandaloneComponent has a dependency on the DataService, which is injected through the constructor.

  1. Provide the dependencies: In the module or component that uses the standalone component, you need to configure the DI provider to make the required dependencies available.

a. Module-level configuration: If the standalone component is part of a module, you can provide the dependencies at the module level by specifying them in the providers array of the module's @NgModule decorator.

import { NgModule } from "@angular/core";
import { CommonModule } from "@angular/common";
import { StandaloneComponent } from "./standalone.component";
import { DataService } from "../services/data.service";

@NgModule({
  declarations: [StandaloneComponent],
  imports: [CommonModule],
  providers: [DataService],
})
export class StandaloneModule {}

In this example, the DataService is provided at the module level, making it available for injection into the StandaloneComponent and any other components or services within the module.

b. Component-level configuration: If the standalone component is not part of a module, you can provide the dependencies directly at the component level using the providers property of the @Component decorator.

import { Component } from "@angular/core";
import { DataService } from "../services/data.service";

@Component({
  selector: "app-standalone",
  templateUrl: "./standalone.component.html",
  styleUrls: ["./standalone.component.css"],
  providers: [DataService],
})
export class StandaloneComponent {}

In this example, the DataService is provided at the component level, making it available for injection into the StandaloneComponent only.

By providing the dependencies, Angular’s DI system will take care of injecting the appropriate instances wherever they are required. This promotes modular and reusable code, as the dependencies can be easily swapped or mocked for testing purposes.

Note: Remember to import the necessary dependencies and ensure they are correctly configured in their respective modules or components.

With proper DI configuration, your standalone component can effectively utilize the required dependencies and maintain loose coupling with other parts of your application.

Conclusion

Indeed, using a standalone component in Angular can simplify your application development.

Standalone components offer flexibility and modularity, allowing you to create reusable components that are not tied to any specific module. By utilizing standalone components, you can reduce the complexity of your Angular project and make it easier to maintain and extend.

Please let me know your feedback on this article. Happy coding!

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