What Is Angular Service?
For more detail kindly refer the link....
Services are commonly used for storing data and
making HTTP calls.
The main idea behind a service is to provide an
easy way to share the data between the components and with the help of dependency
injection (DI) you can control how the service instances are shared.
Services use to fetch the data from the RESTful
API.
How to setup and create services?
Before starting to create a service, you just
need to set up a dev environment.
Install Node.js
and npm if they are not already on your machine.
Then install the Angular CLI globally.
npm
install -g
@angular/cli
Angular CLI tool will allow you to easily and
quickly generate services, components, pipes, and many more files for your
project.
Now, create a new project using the CLI command -
ng new
MyProject
And go to your created project directory and
launch the server.
ng serve
--open
Now come to service - execute below the command
for generating service class.
ng g
service MyService
It will create the two files in the folder -
src/app/
1. my-service.service.spec.ts
2. my-service.service.ts
Now, import my service file into the angular
module - app.module.ts file. It looks like this.
import
{ AppComponent } from
'./app.component';
import
{MyService} from
'./my-service.service';//Import
Service
//AppModule class with @NgModule
decorator
@NgModule({
//Static, This is the compiler configuration
//declarations is used for configure the selectors.
declarations: [
AppComponent
],
//Composability and Grouping
//imports used for composing NgModules together.
imports: [
BrowserModule
],
//Runtime or injector configuration
//providers is used for runtime injector
configuration.
providers: [MyService],
//bootstrapped entry component
bootstrap: [AppComponent]
})
export
class AppModule
{ }
And let’s see the created service class -my-service.service.ts
import
{ Injectable } from
'@angular/core';
@Injectable()
export
class MyService
{
constructor() { }
}
Now you need to create service methods to get,
post, put, and delete the users.
import
{ Injectable } from
'@angular/core';
@Injectable()
export
class MyService
{
constructor() { }
//I’m using the static data
//You can also fetch the data using HttpClient
service for backend APIs.
users = [
{ "id":
1, "name":
"Anil Singh",
'age' :32
},
{ "id":
2, "name":
"Aradhya"
, 'age' :32},
{ "id":
3, "name":
"Reena Singh"
, 'age' :32}
]
/* (method) MyService.getUsers(): {
"id": number;
"name": string;
'age': number;
}[] */
getUsers(){
return this.users;
}
}
Now, use this service in the user component for
display on UI - my-user.component.ts
import
{ Component, OnInit
} from '@angular/core';
import
{MyService} from
'../my-service.service';
@Component({
selector: 'app-my-user',
templateUrl: './my-user.component.html',
styleUrls: ['./my-user.component.css']
})
export
class MyUserComponent
implements OnInit
{
userList =[];
constructor(private
service :MyService)
{
//Get the user list by using the my service.
this.userList
= service.getUsers();
}
ngOnInit() { }
}
And my-user.component.html
<h4>User
List -</h4>
<table
border="1">
<tr>
<th>ID</th><th>Name</th><th>Age</th>
</tr>
<tr *ngFor="let
user of userList">
<td>{{user.id}}</td><td>{{user.name}}</td><td>{{user.Age}}</td>
</tr>
</table>
Finally, you got the user list on your components
HTML.
What Is Singleton Service?
In Angular, two ways to make a singleton service
-
1. Include
the service in the AppModule
2. Declare
that the service should be provided in the application root.
The preferred way to create a singleton service -
Form beginning to Angular 6 is –
import
{ Injectable } from
'@angular/core';
@Injectable({
providedIn: 'root',
})
export
class CustomerService
{
}
Another way to create a singleton service - Include
service in the AppModule
customer.service.ts –
import
{ Injectable } from
'@angular/core';
@Injectable()
export
class CustomersService
{
constructor() { }
}
And app.module.ts -
import
{CustomerService} from
'./customers.service';
//AppModule class with @NgModule
decorator
@NgModule({
//Static, this is the compiler configuration
//declarations is used for configure the selectors.
declarations: [
AppComponent
],
//Composability and Grouping
//imports used for composing NgModules together.
imports: [
BrowserModule
],
//Runtime or injector configuration
//providers is used for runtime injector
configuration.
providers: [CustomerService],
//bootstrapped entry component
bootstrap: [AppComponent]
})
export
class AppModule
{ }