Creating components with CLI in Angular - Try It Yourself

Creating Angular Components with CLI

📖 Scenario: You are building a simple Angular app for a local library. You want to create a component to show book details.

🎯 Goal: Learn how to create an Angular component using the Angular CLI and set it up in your app.

📋 What You'll Learn

Use Angular CLI to generate a component named book-details

Add a configuration variable showDetails in the component TypeScript file

Use the showDetails variable in the component template to conditionally show book information

Include the book-details component selector in the main app component template

💡 Why This Matters

🌍 Real World

Creating reusable UI parts in Angular apps is common for building interactive web pages.

💼 Career

Knowing how to generate and use components with Angular CLI is a fundamental skill for Angular developers.

1

Generate the book-details component using Angular CLI

Use the Angular CLI command ng generate component book-details to create a new component called book-details.

Angular

# Run the Angular CLI command to generate the component
# Your code here

Hint

Open your terminal and type ng generate component book-details to create the component files.

2

Add a showDetails boolean variable in book-details.component.ts

In the book-details.component.ts file, add a public boolean variable called showDetails and set it to true.

Angular

export class BookDetailsComponent {
  // Add a public boolean variable showDetails set to true
  // Your code here
}

Hint

Inside the BookDetailsComponent class, write public showDetails: boolean = true;

3

Use showDetails in the component template to conditionally display book info

In the book-details.component.html file, add an <h2> with text Book Title: Angular Basics that only shows if showDetails is true using Angular's *ngIf directive.

Angular

 with text 'Book Title: Angular Basics' that shows only if showDetails is true -->

Hint

Use <h2 *ngIf="showDetails">Book Title: Angular Basics</h2> in the template.

4

Add the book-details component selector to the main app template

In the app.component.html file, add the <app-book-details></app-book-details> tag to display the book details component.

Angular

 tag to include the book-details component -->

Hint

Insert <app-book-details></app-book-details> in app.component.html.

Practice

1. What command do you use to create a new Angular component using the CLI?

easy

A. ng build component component-name

B. ng create component component-name

C. ng new component component-name

D. ng generate component component-name

Solution

1. Step 1: Understand Angular CLI commands

   The Angular CLI uses ng generate to create new files and features.

2. Step 2: Identify the correct syntax for creating components

   To create a component, the command is ng generate component followed by the component name.

3. Final Answer:

   ng generate component component-name -> Option D

4. Quick Check:

   Use ng generate component to create components [OK]

Hint: Remember: 'generate' creates, 'create' is incorrect here [OK]

Common Mistakes:

• Using 'ng create' instead of 'ng generate'
• Confusing 'ng new' which creates a new project
• Using 'ng build' which compiles the app

2. Which of the following is the correct syntax to generate a component named header using Angular CLI?

easy

A. ng generate component header

B. ng generate component-header

C. ng generate component:header

D. ng generate component/header

Solution

1. Step 1: Check the correct command format

   The Angular CLI expects the component name as a simple argument after the command.

2. Step 2: Identify the valid component name format

   Component names should be simple words or camelCase without special characters like ':' or '/'.

3. Final Answer:

   ng generate component header -> Option A

4. Quick Check:

   Use space, not symbols, between command and name [OK]

Hint: Use space after 'component' for name, no symbols [OK]

Common Mistakes:

• Using symbols like ':' or '/' in component name
• Hyphenating the command instead of the name
• Confusing command syntax with file paths

3. What files are created when you run ng generate component footer in an Angular project?

medium

A. footer.component.js, footer.component.html, footer.component.css

B. footer.ts, footer.html, footer.css, footer.spec.ts

C. footer.component.ts, footer.component.html, footer.component.css, footer.component.spec.ts

D. footer.component.ts, footer.html, footer.css, footer.spec.js

Solution

1. Step 1: Recall Angular component file structure

   Angular components generate four files: TypeScript, HTML, CSS, and a test spec file, all with the component name prefix.

2. Step 2: Match the correct file extensions and naming

   The files have extensions .ts, .html, .css, and .spec.ts with the component name and '.component' in the filename.

3. Final Answer:

   footer.component.ts, footer.component.html, footer.component.css, footer.component.spec.ts -> Option C

4. Quick Check:

   Angular components create 4 files with .component and correct extensions [OK]

Hint: Remember 4 files: .ts, .html, .css, .spec.ts [OK]

Common Mistakes:

• Missing the .spec.ts test file
• Using .js instead of .ts
• Omitting '.component' in filenames

4. You ran ng generate component nav-bar but got an error. What is the likely cause?

medium

A. You must run the command inside an Angular project folder

B. Component names cannot contain hyphens

C. The CLI command should be ng create component nav-bar

D. Component names must be uppercase

Solution

1. Step 1: Check the environment for running CLI commands

   Angular CLI commands must be run inside an Angular project folder where configuration files exist.

2. Step 2: Verify the command syntax and naming rules

   Hyphens are allowed in component names, and the command is ng generate component, not ng create. Component names can be lowercase.

3. Final Answer:

   You must run the command inside an Angular project folder -> Option A

4. Quick Check:

   Run CLI commands inside Angular project folder [OK]

Hint: Always run CLI commands inside your Angular project folder [OK]

Common Mistakes:

• Trying to run commands outside the project folder
• Using 'ng create' instead of 'ng generate'
• Thinking hyphens are invalid in names

5. You want to create a component named userProfile inside a folder features using Angular CLI. Which command correctly does this?

hard

A. ng generate component features userProfile

B. ng generate component features/userProfile

C. ng generate component features-userProfile

D. ng generate component userProfile/features

Solution

1. Step 1: Understand folder structure in CLI commands

   To create a component inside a folder, specify the folder path before the component name separated by a slash.

2. Step 2: Identify the correct command syntax

   The correct syntax is ng generate component features/userProfile to place the component inside the 'features' folder.

3. Final Answer:

   ng generate component features/userProfile -> Option B

4. Quick Check:

   Use slash to specify folder path before component name [OK]

Hint: Use folder/componentName with slash to create nested components [OK]

Common Mistakes:

• Swapping folder and component name order
• Using space instead of slash for folder path
• Hyphenating folder and component name incorrectly