Creating a service with CLI in Angular - Visual Walkthrough

Concept Flow - Creating a service with CLI

Open Terminal

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Run CLI Command

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Angular CLI Generates Service Files

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Service File Created

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Import Service in Component

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Use Service in Component Code

This flow shows how you open a terminal, run the Angular CLI command to create a service, then import and use it in your component.

Execution Sample

Angular

ng generate service data

// or shorthand
ng g s data

This command creates a new Angular service named 'data' with the CLI.

Execution Table

Step	Action	CLI Output	Resulting Files
1	Open terminal in Angular project folder	No output	No files created
2	Run 'ng generate service data'	CREATE src/app/data.service.ts CREATE src/app/data.service.spec.ts	data.service.ts, data.service.spec.ts created
3	Check data.service.ts content	Contains @Injectable decorator and class DataService	Service ready to use
4	Import DataService in a component	No CLI output	Component updated with import statement
5	Inject DataService in component constructor	No CLI output	Service instance available in component
6	Use service methods in component	No CLI output	Component can call service functions
7	Exit	Process complete	Service fully integrated

💡 Service files created and ready to be used in components

Variable Tracker

Variable	Start	After Step 2	After Step 4	After Step 5	Final
data.service.ts	Not present	Created by CLI	Imported in component	Injected in constructor	Used in component methods
Component	No service import	No change	Import added	Constructor updated	Calls service methods

Key Moments - 3 Insights

Why do we run 'ng generate service data' in the terminal?

Running this CLI command automatically creates the service files with correct structure and boilerplate, as shown in execution_table step 2.

What does the CLI create when generating a service?

The CLI creates a TypeScript service file and a test file, as seen in execution_table step 2, ensuring you have both code and tests ready.

How do we make the service usable inside a component?

By importing the service file and injecting it in the component constructor, as shown in execution_table steps 4 and 5.

Visual Quiz - 3 Questions

Look at the execution table, what files are created after running the CLI command?

A app.module.ts and main.ts

B data.component.ts and data.component.html

C data.service.ts and data.service.spec.ts

D index.html and styles.css

💡 Hint

Check execution_table row 2 under 'Resulting Files'

At which step is the service imported into a component?

A Step 4

B Step 2

C Step 6

D Step 1

💡 Hint

Look at execution_table row 4 under 'Action'

If you skip injecting the service in the constructor, what happens?

A The CLI will create the service again

B The service methods cannot be used in the component

C The component will automatically find the service

D The service file will be deleted

💡 Hint

Refer to variable_tracker for 'Component' variable after Step 5

Concept Snapshot

Angular CLI service creation:
- Run 'ng generate service name' in terminal
- CLI creates service and test files
- Import service in component
- Inject service in constructor
- Use service methods in component code

Full Transcript

To create a service in Angular using the CLI, open your terminal in the Angular project folder. Run the command 'ng generate service data' or 'ng g s data' for short. The CLI creates two files: data.service.ts and data.service.spec.ts. The service file contains a class decorated with @Injectable, ready to provide functionality. Next, import this service into your component by adding an import statement. Then inject the service in the component's constructor to make it available. Finally, you can call the service's methods inside your component. This process automates service creation and integration, saving time and avoiding errors.