Migrating from NgModules in Angular - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

Standalone Component Import Behavior

Consider an Angular standalone component ProfileCard that you want to use inside another standalone component Dashboard. How should you import ProfileCard into Dashboard to display it correctly?

Angular

import { Component } from '@angular/core';
import { ProfileCard } from './profile-card.component';

@Component({
  selector: 'app-dashboard',
  standalone: true,
  imports: [/* What goes here? */],
  template: `<app-profile-card></app-profile-card>`
})
export class Dashboard {}

A Declare ProfileCard in the declarations array of Dashboard's NgModule.

B Add ProfileCard to the imports array in the @Component decorator of Dashboard.

C Add ProfileCard to the providers array in Dashboard component.

D No import needed; Angular automatically detects standalone components.

💡 Hint

Standalone components must be explicitly imported in the imports array of the component using them.

Standalone components are imported via the imports array in the @Component decorator. Unlike NgModules, you do not declare them in declarations or providers.

📝 Syntax

intermediate

Correct Syntax for Standalone Component Declaration

Which of the following is the correct way to declare a standalone Angular component named AlertBox?

A @Component({ selector: 'app-alert-box', standalone: true, template: `<p>Alert!</p>` }) export class AlertBox {}

B @Component({ selector: 'app-alert-box', standalone: true }) export class AlertBox {}

C @Component({ selector: 'app-alert-box', standalone: true, templateUrl: 'alert-box.html' }) export class AlertBox {}

D @Component({ selector: 'app-alert-box', standalone: false, template: `<p>Alert!</p>` }) export class AlertBox {}

💡 Hint

Standalone components require the standalone flag set to true and a template or templateUrl.

Option A correctly sets standalone: true and provides an inline template. Option A has standalone false, so it's not standalone. Option A uses templateUrl but does not specify the file extension properly (missing quotes or path). Option A lacks a template or templateUrl, so it will cause an error.

🔧 Debug

advanced

Error When Using a Standalone Component Without Import

You have a standalone component UserCard and a standalone component AppRoot. You use <app-user-card> inside AppRoot template but forget to import UserCard in AppRoot. What error will Angular throw at runtime?

A No error; Angular automatically resolves standalone components

B NullInjectorError: No provider for UserCard

C SyntaxError: Unexpected token '<' in template

D Template parse error: 'app-user-card' is not a known element

💡 Hint

Angular needs components to be imported to recognize their selectors in templates.

If a standalone component is used in a template but not imported, Angular cannot recognize its selector and throws a template parse error.

❓ state_output

advanced

Effect of Removing NgModule on Service Injection

You migrate a feature module to standalone components and remove its NgModule. You have a service DataService provided in the removed module. What happens to the service injection in components that used to rely on that module?

A Service injection fails with No provider error unless the service is provided elsewhere.

B Service injection continues to work because Angular automatically provides services globally.

C Service injection works only if the service is provided in the component's providers array.

D Service injection works only if the service is provided in the root injector.

💡 Hint

Removing the NgModule removes its providers unless they are moved or provided elsewhere.

When you remove an NgModule, any services provided in it are no longer available unless you provide them in standalone components or at root level.

🧠 Conceptual

expert

Advantages of Standalone Components Over NgModules

Which of the following is NOT an advantage of migrating from NgModules to standalone components in Angular?

A Simplifies component dependencies by importing only what is needed directly in components.

B Eliminates the need for NgModule metadata, reducing boilerplate code.

C Automatically improves runtime performance by lazy loading all components.

D Enables easier tree-shaking and smaller bundle sizes.

💡 Hint

Consider what standalone components change and what they do not automatically do.

Standalone components simplify imports and reduce boilerplate, improving tree-shaking. However, lazy loading is a separate feature and not automatically applied to all standalone components.