Services are used to create variables/data that can be shared and can be used outside the component in which it is defined.

• STEP #1: Creating a service:-

  ng g s service-name

  s is a short-form for service.This creates two files service-name.service.spec.ts which is not supposed to be changed and a service-name.service.ts.

• STEP #2: After the service is created, we have to include it in the providers of app.module.ts
  providers: [Service-nameService],

  here, the first letter of the service-name should be capital followed by Service written without any space.

• STEP #3: So we have to now make changes in service-name.service.ts create a json variable which is supposed to be made available to various components
  Sailors = [22, ‘Dustin’, 7];
  Sailors variable here is an array.
• STEP #4: In app.component.ts make the following changes:
  import the service among the rest of the required imports
  Example:-

  import { Service-nameService } from './service-name.service';

  just like the way we did it in providers.

  Create a variable of any type: newData without mentioning any type
  In constructor define a property of the Service type

  constructor(private demoService: ServiceService) {}

  Also create an ngOnInit method:

      ngOnInit(): void {
      this.newData=this.demoService.Sailors;
  

• STEP #5: In app.component.html we will print the data stored in newData :

  {{newData}}

Note: As we have added ngFor in app.component.html we will have to import FormsModule in app.module.ts






Syntax (Example #1):
serice.service.ts








import { Injectable } from '@angular/core';    @Injectable({   providedIn: 'root' }) export class ServiceService {      Sailors = [     {       id: 22, name: 'Dustin', rating: 7     },     {        id: 29, name: 'Brutus', rating: 1     },     {       id: 31, name: 'Lubber', rating: 8     },     {       id: 32, name: 'Andy', rating: 8     },     {       id: 58, name: 'Rusty', rating: 10     },     {       id: 64, name: 'Horatio', rating: 7     },     {       id: 71, name: 'Zorba', rating: 10     },     {       id: 74, name: 'Horatio', rating: 9     }   ];      constructor() { }   getData() {     return 'This is the list of sailors and their corresponding ratings';   } }

In app.component.ts








import { Component } from '@angular/core'; import { ServiceService } from './service.service'; @Component({   selector: 'app-root',   templateUrl: './app.component.html',   styleUrls: ['./app.component.css'] }) export class AppComponent {   newData;   message:string='';   constructor(private demoService: ServiceService) {}   ngOnInit(): void {     this.newData=this.demoService.Sailors;     this.message=this.demoService.getData();   } }

app.component.html








<b>Service Example</b> <h5>{{ message }}</h5> <p> ID Name Rating</p> <div *ngFor="let m of newData;">     <p>{{m.id}} {{m.name}} {{m.rating}}</p> </div>

Output:


References:
https://coursetro.com/posts/code/61/Angular-4-Services-Tutorial

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