http observable sample

README.md

1. On the root module (app.module.ts)

   • import the HttpClientModule
   • put it in the imports section

2. On the app.service.ts

   • import the HttpClient from @angular/common/http
   • Inject it in the constructor of the service

3. In angular.json

   • Under architect > build > options > assets, add "src/api"

4. Inside the src folder

   • create a folder named "api"
   • insie the "api" folder, put the file "books.json"

angular.json

{
  "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
  "version": 1,
  "newProjectRoot": "projects",
  "projects": {
    "http": {
      "root": "",
      "sourceRoot": "src",
      "projectType": "application",
      "prefix": "app",
      "schematics": {},
      "architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            "outputPath": "dist/http",
            "index": "src/index.html",
            "main": "src/main.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.app.json",
            "assets": [
              "src/favicon.ico",
              "src/assets",
              "src/api"
            ],
            "styles": [
              "src/styles.css"
            ],
            "scripts": []
          },
          "configurations": {
            "production": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "optimization": true,
              "outputHashing": "all",
              "sourceMap": false,
              "extractCss": true,
              "namedChunks": false,
              "aot": true,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true,
              "budgets": [
                {
                  "type": "initial",
                  "maximumWarning": "2mb",
                  "maximumError": "5mb"
                }
              ]
            }
          }
        },
        "serve": {
          "builder": "@angular-devkit/build-angular:dev-server",
          "options": {
            "browserTarget": "http:build"
          },
          "configurations": {
            "production": {
              "browserTarget": "http:build:production"
            }
          }
        },
        "extract-i18n": {
          "builder": "@angular-devkit/build-angular:extract-i18n",
          "options": {
            "browserTarget": "http:build"
          }
        },
        "test": {
          "builder": "@angular-devkit/build-angular:karma",
          "options": {
            "main": "src/test.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.spec.json",
            "karmaConfig": "src/karma.conf.js",
            "styles": [
              "src/styles.css"
            ],
            "scripts": [],
            "assets": [
              "src/favicon.ico",
              "src/assets",
              "src/api"
            ]
          }
        },
        "lint": {
          "builder": "@angular-devkit/build-angular:tslint",
          "options": {
            "tsConfig": [
              "src/tsconfig.app.json",
              "src/tsconfig.spec.json"
            ],
            "exclude": [
              "**/node_modules/**"
            ]
          }
        }
      }
    },
    "http-e2e": {
      "root": "e2e/",
      "projectType": "application",
      "prefix": "",
      "architect": {
        "e2e": {
          "builder": "@angular-devkit/build-angular:protractor",
          "options": {
            "protractorConfig": "e2e/protractor.conf.js",
            "devServerTarget": "http:serve"
          },
          "configurations": {
            "production": {
              "devServerTarget": "http:serve:production"
            }
          }
        },
        "lint": {
          "builder": "@angular-devkit/build-angular:tslint",
          "options": {
            "tsConfig": "e2e/tsconfig.e2e.json",
            "exclude": [
              "**/node_modules/**"
            ]
          }
        }
      }
    }
  },
  "defaultProject": "http"
}

app.component.html

<h1>{{ title }}</h1>

<ul>
  <li *ngFor="let b of books">
    {{ b.title }} - {{ b.author}}
  </li>
</ul>

app.component.ts

import { Component, OnInit } from '@angular/core';
import { BookService } from './app.service';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {

  title = 'http';
  books: any[];
  errorMessage:any;

  constructor(private bookservice: BookService) {}

  ngOnInit() {
    this.bookservice.getBooks().subscribe(
      book => {
        this.books = book
      },
      error => this.errorMessage = <any>error
    );
  }
}

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { HttpClientModule } from '@angular/common/http';


@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    HttpClientModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

app.service.ts

import { Injectable } from "@angular/core";
import { Observable } from "rxjs";
import { tap } from "rxjs/operators";
import { HttpClient } from "@angular/common/http";

@Injectable({
  providedIn: 'root'
})
export class BookService {
  
  private bookurl = 'api/books.json'; 

  constructor(private http: HttpClient) {}

  getBooks():Observable<any> {
    return this.http.get(this.bookurl).pipe(
      tap(data => console.log(JSON.stringify(data)))
    );
  }
}

books.json

[
{   
  "title": "War and Peace",
    "author": "Leo Tolstoy",
    "price": 15,
    "rating": 4.5
  },
  {
    "title": "Nicholas Nickleby",
    "author": "Charles Dickens",
    "price": 12,
    "rating": 3.5
  },
  {
    "title": "Memoirs of Sherlock Holmes",
    "author": "Arthur Conan Doyle",
    "price": 35,
    "rating": 5
  },
  {
    "title": "Scarlet Letter",
    "author": "Nathaniel Hawthorne",
    "price": 12,
    "rating": 3
  },
  {
    "title": "Don Quixote",
    "author": "Cervantes",
    "price": 20,
    "rating": 4
  }
]