Creating a service with CLI in Angular - Practice Exercises

Challenge - 5 Problems

📝 Syntax

intermediate

What is the correct Angular CLI command to create a service named user?

Choose the exact Angular CLI command that generates a service named user in the default folder.

A ng create service user

B ng generate service user

C ng new service user

D ng make service user

💡 Hint

The Angular CLI uses generate or its shorthand g to create new files.

The correct command to create a service is ng generate service user. The other commands are invalid Angular CLI commands.

❓ component_behavior

intermediate

What will be the providedIn scope of a service created with ng generate service user by default?

After running ng generate service user, what is the default providedIn value in the generated service's decorator?

A providedIn: 'platform'

B No providedIn property is set by default

C providedIn: 'any'

D providedIn: 'root'

💡 Hint

Angular services are usually provided at the root level for app-wide singleton behavior.

By default, Angular CLI adds providedIn: 'root' to the service decorator. This makes the service available app-wide as a singleton.

🔧 Debug

advanced

Why does this Angular CLI command fail? ng generate service

You run ng generate service without any name. What error will Angular CLI show?

A Error: Service already exists

B No error, service created with default name

C Error: Missing required argument: name

D Error: Invalid command syntax

💡 Hint

The CLI needs a name to create a service file.

The Angular CLI requires a service name argument. Running ng generate service alone causes an error about missing the required name argument.

❓ state_output

advanced

What files are created by ng generate service auth?

Select the exact files generated by Angular CLI when creating a service named auth.

A auth.service.ts and auth.service.spec.ts

B auth.service.ts only

C auth.ts and auth.spec.ts

D auth.service.ts, auth.service.spec.ts, and auth.module.ts

💡 Hint

Angular CLI generates a TypeScript file and a test spec file for services.

By default, Angular CLI creates two files: auth.service.ts and auth.service.spec.ts for the service and its tests.

🧠 Conceptual

expert

Which Angular CLI command creates a service in a specific folder shared with the name logger?

You want to create a service named logger inside the src/app/shared folder using Angular CLI. Which command is correct?

A ng generate service shared/logger

B ng generate service logger/shared

C ng generate service logger --folder=shared

D ng generate service --path=shared logger

💡 Hint

Use the folder path before the service name separated by a slash.

The correct syntax is ng generate service shared/logger. The CLI interprets the path before the slash as the folder and the last part as the service name.

Practice

1. What is the main purpose of creating a service in Angular using the CLI?

easy

A. To generate routing modules

B. To share logic and data across multiple components

C. To style components with CSS

D. To create new components automatically

Solution

1. Step 1: Understand Angular services role

   Services in Angular are used to share logic and data between components, avoiding duplication.

2. Step 2: Recognize CLI service creation purpose

   The CLI command generates a service file with proper structure to be injected and reused.

3. Final Answer:

   To share logic and data across multiple components -> Option B

4. Quick Check:

   Services share logic/data = D [OK]

Hint: Services share data/logic, not create components [OK]

Common Mistakes:

• Confusing services with components
• Thinking services handle styling
• Assuming services generate routing

2. Which Angular CLI command correctly creates a new service named data?

easy

A. ng new service data

B. ng create service data

C. ng generate service data

D. ng make service data

Solution

1. Step 1: Recall Angular CLI syntax for services

   The correct command to generate a service is ng generate service [name].

2. Step 2: Match the command with options

   Only ng generate service data uses the correct ng generate service syntax.

3. Final Answer:

   ng generate service data -> Option C

4. Quick Check:

   Use ng generate service for services [OK]

Hint: Use 'ng generate service' to create services [OK]

Common Mistakes:

• Using 'ng create' instead of 'ng generate'
• Confusing 'ng new' for service creation
• Typing 'ng make' which is invalid

3. Given the command ng generate service user, what files are created by default?

medium

A. user.component.ts and user.component.html

B. user.service.js and user.service.test.js

C. user.module.ts and user-routing.module.ts

D. user.service.ts and user.service.spec.ts

Solution

1. Step 1: Understand CLI output for service generation

   The Angular CLI creates a TypeScript service file and a test spec file by default.

2. Step 2: Identify correct file extensions and names

   Files are named user.service.ts and user.service.spec.ts, matching user.service.ts and user.service.spec.ts.

3. Final Answer:

   user.service.ts and user.service.spec.ts -> Option D

4. Quick Check:

   Service + test files = B [OK]

Hint: Service files end with .service.ts and .service.spec.ts [OK]

Common Mistakes:

• Confusing service files with component files
• Expecting .js or .test.js extensions
• Thinking routing or module files are created

4. You ran ng generate service auth but got an error: Unknown command: 'generatee'. What is the likely cause?

medium

A. Typo in the command: 'generatee' instead of 'generate'

B. Service name 'auth' is invalid

C. Angular CLI is not installed

D. Missing --service flag

Solution

1. Step 1: Analyze the error message

   The error says 'Unknown command: generatee', indicating a typo in the command.

2. Step 2: Check command spelling

   The correct command is 'generate', not 'generatee'. This typo causes the error.

3. Final Answer:

   Typo in the command: 'generatee' instead of 'generate' -> Option A

4. Quick Check:

   Check spelling of CLI commands carefully [OK]

Hint: Check command spelling carefully for typos [OK]

Common Mistakes:

• Typing 'generatee' instead of 'generate'
• Assuming service name causes error
• Thinking CLI is missing when it is installed

5. You want to create a service named logger inside a folder shared/utils using Angular CLI. Which command is correct?

hard

A. ng generate service shared/utils/logger

B. ng generate service logger/shared/utils

C. ng generate service shared-utils-logger

D. ng generate service /shared/utils/logger

Solution

1. Step 1: Understand CLI path syntax for nested folders

   Angular CLI uses slash-separated paths to place files in nested folders.

2. Step 2: Identify correct command format

   ng generate service shared/utils/logger correctly uses shared/utils/logger to create the service in nested folders.

3. Final Answer:

   ng generate service shared/utils/logger -> Option A

4. Quick Check:

   Use slash paths for nested service folders [OK]

Hint: Use folder paths with slashes before service name [OK]

Common Mistakes:

• Reversing folder and service name order
• Using dashes instead of slashes for folders
• Starting path with a slash causing errors