Handling HTTP Request using RxJs in Angular

Handling HTTP request in an Angular application is a crucial part. In this article we will go through below methods from RxJs to handle HTTP requests.

1. map → applies the function supplied to each value of input observable and emits the resulting value as observable.
2. mergeMap or flatMap → allows us to flatten multiple separate subscribed Observable into a single cohesive stream, which we can use to control events coming from user input and from server responses.
3. switchMap → Projects each source value to an Observable which is merged in the output Observable, emitting values only from the most recently projected Observable.
4. forkJoin → Accepts an Array of ObservableInput or a dictionary Object of ObservableInput and returns an Observable that emits either an array of values in the exact same order as the passed array, or a dictionary of values in the same shape as the passed dictionary.

map

Use case: One use case could be we want to convert all observables into observables of JSON objects.

signature: map<T, R>(project: (value: T, index: number) => R, thisArg?: any): OperatorFunction<T, R>

#angular #front-end-development #rxjs #http-request

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Pdf2gerb: Perl Script Converts PDF Files to Gerber format

pdf2gerb

Perl script converts PDF files to Gerber format

Pdf2Gerb generates Gerber 274X photoplotting and Excellon drill files from PDFs of a PCB. Up to three PDFs are used: the top copper layer, the bottom copper layer (for 2-sided PCBs), and an optional silk screen layer. The PDFs can be created directly from any PDF drawing software, or a PDF print driver can be used to capture the Print output if the drawing software does not directly support output to PDF.

The general workflow is as follows:

1. Design the PCB using your favorite CAD or drawing software.
2. Print the top and bottom copper and top silk screen layers to a PDF file.
3. Run Pdf2Gerb on the PDFs to create Gerber and Excellon files.
4. Use a Gerber viewer to double-check the output against the original PCB design.
5. Make adjustments as needed.
6. Submit the files to a PCB manufacturer.

Please note that Pdf2Gerb does NOT perform DRC (Design Rule Checks), as these will vary according to individual PCB manufacturer conventions and capabilities. Also note that Pdf2Gerb is not perfect, so the output files must always be checked before submitting them. As of version 1.6, Pdf2Gerb supports most PCB elements, such as round and square pads, round holes, traces, SMD pads, ground planes, no-fill areas, and panelization. However, because it interprets the graphical output of a Print function, there are limitations in what it can recognize (or there may be bugs).

See docs/Pdf2Gerb.pdf for install/setup, config, usage, and other info.

---

pdf2gerb_cfg.pm

#Pdf2Gerb config settings:
#Put this file in same folder/directory as pdf2gerb.pl itself (global settings),
#or copy to another folder/directory with PDFs if you want PCB-specific settings.
#There is only one user of this file, so we don't need a custom package or namespace.
#NOTE: all constants defined in here will be added to main namespace.
#package pdf2gerb_cfg;

use strict; #trap undef vars (easier debug)
use warnings; #other useful info (easier debug)


##############################################################################################
#configurable settings:
#change values here instead of in main pfg2gerb.pl file

use constant WANT_COLORS => ($^O !~ m/Win/); #ANSI colors no worky on Windows? this must be set < first DebugPrint() call

#just a little warning; set realistic expectations:
#DebugPrint("${\(CYAN)}Pdf2Gerb.pl ${\(VERSION)}, $^O O/S\n${\(YELLOW)}${\(BOLD)}${\(ITALIC)}This is EXPERIMENTAL software.  \nGerber files MAY CONTAIN ERRORS.  Please CHECK them before fabrication!${\(RESET)}", 0); #if WANT_DEBUG

use constant METRIC => FALSE; #set to TRUE for metric units (only affect final numbers in output files, not internal arithmetic)
use constant APERTURE_LIMIT => 0; #34; #max #apertures to use; generate warnings if too many apertures are used (0 to not check)
use constant DRILL_FMT => '2.4'; #'2.3'; #'2.4' is the default for PCB fab; change to '2.3' for CNC

use constant WANT_DEBUG => 0; #10; #level of debug wanted; higher == more, lower == less, 0 == none
use constant GERBER_DEBUG => 0; #level of debug to include in Gerber file; DON'T USE FOR FABRICATION
use constant WANT_STREAMS => FALSE; #TRUE; #save decompressed streams to files (for debug)
use constant WANT_ALLINPUT => FALSE; #TRUE; #save entire input stream (for debug ONLY)

#DebugPrint(sprintf("${\(CYAN)}DEBUG: stdout %d, gerber %d, want streams? %d, all input? %d, O/S: $^O, Perl: $]${\(RESET)}\n", WANT_DEBUG, GERBER_DEBUG, WANT_STREAMS, WANT_ALLINPUT), 1);
#DebugPrint(sprintf("max int = %d, min int = %d\n", MAXINT, MININT), 1); 

#define standard trace and pad sizes to reduce scaling or PDF rendering errors:
#This avoids weird aperture settings and replaces them with more standardized values.
#(I'm not sure how photoplotters handle strange sizes).
#Fewer choices here gives more accurate mapping in the final Gerber files.
#units are in inches
use constant TOOL_SIZES => #add more as desired
(
#round or square pads (> 0) and drills (< 0):
    .010, -.001,  #tiny pads for SMD; dummy drill size (too small for practical use, but needed so StandardTool will use this entry)
    .031, -.014,  #used for vias
    .041, -.020,  #smallest non-filled plated hole
    .051, -.025,
    .056, -.029,  #useful for IC pins
    .070, -.033,
    .075, -.040,  #heavier leads
#    .090, -.043,  #NOTE: 600 dpi is not high enough resolution to reliably distinguish between .043" and .046", so choose 1 of the 2 here
    .100, -.046,
    .115, -.052,
    .130, -.061,
    .140, -.067,
    .150, -.079,
    .175, -.088,
    .190, -.093,
    .200, -.100,
    .220, -.110,
    .160, -.125,  #useful for mounting holes
#some additional pad sizes without holes (repeat a previous hole size if you just want the pad size):
    .090, -.040,  #want a .090 pad option, but use dummy hole size
    .065, -.040, #.065 x .065 rect pad
    .035, -.040, #.035 x .065 rect pad
#traces:
    .001,  #too thin for real traces; use only for board outlines
    .006,  #minimum real trace width; mainly used for text
    .008,  #mainly used for mid-sized text, not traces
    .010,  #minimum recommended trace width for low-current signals
    .012,
    .015,  #moderate low-voltage current
    .020,  #heavier trace for power, ground (even if a lighter one is adequate)
    .025,
    .030,  #heavy-current traces; be careful with these ones!
    .040,
    .050,
    .060,
    .080,
    .100,
    .120,
);
#Areas larger than the values below will be filled with parallel lines:
#This cuts down on the number of aperture sizes used.
#Set to 0 to always use an aperture or drill, regardless of size.
use constant { MAX_APERTURE => max((TOOL_SIZES)) + .004, MAX_DRILL => -min((TOOL_SIZES)) + .004 }; #max aperture and drill sizes (plus a little tolerance)
#DebugPrint(sprintf("using %d standard tool sizes: %s, max aper %.3f, max drill %.3f\n", scalar((TOOL_SIZES)), join(", ", (TOOL_SIZES)), MAX_APERTURE, MAX_DRILL), 1);

#NOTE: Compare the PDF to the original CAD file to check the accuracy of the PDF rendering and parsing!
#for example, the CAD software I used generated the following circles for holes:
#CAD hole size:   parsed PDF diameter:      error:
#  .014                .016                +.002
#  .020                .02267              +.00267
#  .025                .026                +.001
#  .029                .03167              +.00267
#  .033                .036                +.003
#  .040                .04267              +.00267
#This was usually ~ .002" - .003" too big compared to the hole as displayed in the CAD software.
#To compensate for PDF rendering errors (either during CAD Print function or PDF parsing logic), adjust the values below as needed.
#units are pixels; for example, a value of 2.4 at 600 dpi = .0004 inch, 2 at 600 dpi = .0033"
use constant
{
    HOLE_ADJUST => -0.004 * 600, #-2.6, #holes seemed to be slightly oversized (by .002" - .004"), so shrink them a little
    RNDPAD_ADJUST => -0.003 * 600, #-2, #-2.4, #round pads seemed to be slightly oversized, so shrink them a little
    SQRPAD_ADJUST => +0.001 * 600, #+.5, #square pads are sometimes too small by .00067, so bump them up a little
    RECTPAD_ADJUST => 0, #(pixels) rectangular pads seem to be okay? (not tested much)
    TRACE_ADJUST => 0, #(pixels) traces seemed to be okay?
    REDUCE_TOLERANCE => .001, #(inches) allow this much variation when reducing circles and rects
};

#Also, my CAD's Print function or the PDF print driver I used was a little off for circles, so define some additional adjustment values here:
#Values are added to X/Y coordinates; units are pixels; for example, a value of 1 at 600 dpi would be ~= .002 inch
use constant
{
    CIRCLE_ADJUST_MINX => 0,
    CIRCLE_ADJUST_MINY => -0.001 * 600, #-1, #circles were a little too high, so nudge them a little lower
    CIRCLE_ADJUST_MAXX => +0.001 * 600, #+1, #circles were a little too far to the left, so nudge them a little to the right
    CIRCLE_ADJUST_MAXY => 0,
    SUBST_CIRCLE_CLIPRECT => FALSE, #generate circle and substitute for clip rects (to compensate for the way some CAD software draws circles)
    WANT_CLIPRECT => TRUE, #FALSE, #AI doesn't need clip rect at all? should be on normally?
    RECT_COMPLETION => FALSE, #TRUE, #fill in 4th side of rect when 3 sides found
};

#allow .012 clearance around pads for solder mask:
#This value effectively adjusts pad sizes in the TOOL_SIZES list above (only for solder mask layers).
use constant SOLDER_MARGIN => +.012; #units are inches

#line join/cap styles:
use constant
{
    CAP_NONE => 0, #butt (none); line is exact length
    CAP_ROUND => 1, #round cap/join; line overhangs by a semi-circle at either end
    CAP_SQUARE => 2, #square cap/join; line overhangs by a half square on either end
    CAP_OVERRIDE => FALSE, #cap style overrides drawing logic
};
    
#number of elements in each shape type:
use constant
{
    RECT_SHAPELEN => 6, #x0, y0, x1, y1, count, "rect" (start, end corners)
    LINE_SHAPELEN => 6, #x0, y0, x1, y1, count, "line" (line seg)
    CURVE_SHAPELEN => 10, #xstart, ystart, x0, y0, x1, y1, xend, yend, count, "curve" (bezier 2 points)
    CIRCLE_SHAPELEN => 5, #x, y, 5, count, "circle" (center + radius)
};
#const my %SHAPELEN =
#Readonly my %SHAPELEN =>
our %SHAPELEN =
(
    rect => RECT_SHAPELEN,
    line => LINE_SHAPELEN,
    curve => CURVE_SHAPELEN,
    circle => CIRCLE_SHAPELEN,
);

#panelization:
#This will repeat the entire body the number of times indicated along the X or Y axes (files grow accordingly).
#Display elements that overhang PCB boundary can be squashed or left as-is (typically text or other silk screen markings).
#Set "overhangs" TRUE to allow overhangs, FALSE to truncate them.
#xpad and ypad allow margins to be added around outer edge of panelized PCB.
use constant PANELIZE => {'x' => 1, 'y' => 1, 'xpad' => 0, 'ypad' => 0, 'overhangs' => TRUE}; #number of times to repeat in X and Y directions

# Set this to 1 if you need TurboCAD support.
#$turboCAD = FALSE; #is this still needed as an option?

#CIRCAD pad generation uses an appropriate aperture, then moves it (stroke) "a little" - we use this to find pads and distinguish them from PCB holes. 
use constant PAD_STROKE => 0.3; #0.0005 * 600; #units are pixels
#convert very short traces to pads or holes:
use constant TRACE_MINLEN => .001; #units are inches
#use constant ALWAYS_XY => TRUE; #FALSE; #force XY even if X or Y doesn't change; NOTE: needs to be TRUE for all pads to show in FlatCAM and ViewPlot
use constant REMOVE_POLARITY => FALSE; #TRUE; #set to remove subtractive (negative) polarity; NOTE: must be FALSE for ground planes

#PDF uses "points", each point = 1/72 inch
#combined with a PDF scale factor of .12, this gives 600 dpi resolution (1/72 * .12 = 600 dpi)
use constant INCHES_PER_POINT => 1/72; #0.0138888889; #multiply point-size by this to get inches

# The precision used when computing a bezier curve. Higher numbers are more precise but slower (and generate larger files).
#$bezierPrecision = 100;
use constant BEZIER_PRECISION => 36; #100; #use const; reduced for faster rendering (mainly used for silk screen and thermal pads)

# Ground planes and silk screen or larger copper rectangles or circles are filled line-by-line using this resolution.
use constant FILL_WIDTH => .01; #fill at most 0.01 inch at a time

# The max number of characters to read into memory
use constant MAX_BYTES => 10 * M; #bumped up to 10 MB, use const

use constant DUP_DRILL1 => TRUE; #FALSE; #kludge: ViewPlot doesn't load drill files that are too small so duplicate first tool

my $runtime = time(); #Time::HiRes::gettimeofday(); #measure my execution time

print STDERR "Loaded config settings from '${\(__FILE__)}'.\n";
1; #last value must be truthful to indicate successful load


#############################################################################################
#junk/experiment:

#use Package::Constants;
#use Exporter qw(import); #https://perldoc.perl.org/Exporter.html

#my $caller = "pdf2gerb::";

#sub cfg
#{
#    my $proto = shift;
#    my $class = ref($proto) || $proto;
#    my $settings =
#    {
#        $WANT_DEBUG => 990, #10; #level of debug wanted; higher == more, lower == less, 0 == none
#    };
#    bless($settings, $class);
#    return $settings;
#}

#use constant HELLO => "hi there2"; #"main::HELLO" => "hi there";
#use constant GOODBYE => 14; #"main::GOODBYE" => 12;

#print STDERR "read cfg file\n";

#our @EXPORT_OK = Package::Constants->list(__PACKAGE__); #https://www.perlmonks.org/?node_id=1072691; NOTE: "_OK" skips short/common names

#print STDERR scalar(@EXPORT_OK) . " consts exported:\n";
#foreach(@EXPORT_OK) { print STDERR "$_\n"; }
#my $val = main::thing("xyz");
#print STDERR "caller gave me $val\n";
#foreach my $arg (@ARGV) { print STDERR "arg $arg\n"; }

---

Download Details:

Author: swannman
Source Code: https://github.com/swannman/pdf2gerb

License: GPL-3.0 license

#perl 

Handling HTTP Request using RxJs in Angular

Handling HTTP request in an Angular application is a crucial part. In this article we will go through below methods from RxJs to handle HTTP requests.

1. map → applies the function supplied to each value of input observable and emits the resulting value as observable.
2. mergeMap or flatMap → allows us to flatten multiple separate subscribed Observable into a single cohesive stream, which we can use to control events coming from user input and from server responses.
3. switchMap → Projects each source value to an Observable which is merged in the output Observable, emitting values only from the most recently projected Observable.
4. forkJoin → Accepts an Array of ObservableInput or a dictionary Object of ObservableInput and returns an Observable that emits either an array of values in the exact same order as the passed array, or a dictionary of values in the same shape as the passed dictionary.

map

Use case: One use case could be we want to convert all observables into observables of JSON objects.

signature: map<T, R>(project: (value: T, index: number) => R, thisArg?: any): OperatorFunction<T, R>

#angular #front-end-development #rxjs #http-request

Angular Rxjs: Use .map() And Async Pipe (Refactor Your Code)

In this video, we will see how to improve our code using the #rxs map operator and #angular #async pipe.

The components should be clean and minimal and should not have code that manipulates the data. Responsible for data manipulation is a service.
The goal is to prepare our data and return an #observable pipe so that we can use an #async pipe in the template.

code: https://github.com/profanis/codeShotsWithProfanis/tree/13/rxjsMapAndAsyncPipe

#angular #rxjs #observable #map #async

#angular rxjs #angular #angular tutorial #what is angular

Install Angular - Angular Environment Setup Process

Angular is a TypeScript based framework that works in synchronization with HTML, CSS, and JavaScript. To work with angular, domain knowledge of these 3 is required.

1. Installing Node.js and npm
2. Installing Angular CLI
3. Creating workspace
4. Deploying your First App

In this article, you will get to know about the Angular Environment setup process. After reading this article, you will be able to install, setup, create, and launch your own application in Angular. So let’s start!!!

Install Angular in Easy Steps

For Installing Angular on your Machine, there are 2 prerequisites:

• Node.js
• npm Package Manager

Node.js

First you need to have Node.js installed as Angular require current, active LTS or maintenance LTS version of Node.js

Download and Install Node.js version suitable for your machine’s operating system.

Npm Package Manager

Angular, Angular CLI and Angular applications are dependent on npm packages. By installing Node.js, you have automatically installed the npm Package manager which will be the base for installing angular in your system. To check the presence of npm client and Angular version check of npm client, run this command:

1. npm -v

Installing Angular CLI

• Open Terminal/Command Prompt
• To install Angular CLI, run the below command:

1. npm install -g @angular/cli

· After executing the command, Angular CLI will get installed within some time. You can check it using the following command

1. ng --version

Workspace Creation

Now as your Angular CLI is installed, you need to create a workspace to work upon your application. Methods for it are:

• Using CLI
• Using Visual Studio Code

1. Using CLI

To create a workspace:

• Navigate to the desired directory where you want to create your workspace using cd command in the Terminal/Command prompt
• Then in the directory write this command on your terminal and provide the name of the app which you want to create. In my case I have mentioned DataFlair:

1. Ng new YourAppName

• After running this command, it will prompt you to select from various options about the CSS and other functionalities.

• To leave everything to default, simply press the Enter or the Return key.

#angular tutorials #angular cli install #angular environment setup #angular version check #download angular #install angular #install angular cli

How To Handle HTTP Requests In Angular 8 with Observables

In this Angular 8 tutorial, we are going to learn how to handle asynchronous HTTP requests using Observable and RxJS operators.

We are going to create a live country search module in an Angular app. For which we will be taking help of country list api and handle that API with RxJS observables and operators. Final output of this tutorial will look something like below.

The complete code of this tutorial can be found on given below GitHub repository:

If you are an Angular developer or might face problems using the Observables in Angular, then this tutorial will surely help you to understand the easiest way of using Observables in an Angular to manage the HTTP response.

What Does Angular Say About Observables?

Observables provide support for passing messages between publishers and subscribers in your application. Observables offer significant benefits over other techniques for event handling, asynchronous programming, and handling multiple values.
Angular.io

JavaScript Promises VS RxJS Observables

Let’s find out the difference between JavaScript Promises and RxJS Observables:

Check out the detailed explanation on how to use JavaScript Promises in Angular to manage HTTP response?

Install and Configure Angular Project

Let’s start by installing a basic Angular project for the managing Http request with the observables demo app.

ng new angular-http-observables

# Would you like to add Angular routing?
# Select n and Hit Enter.

# Which stylesheet format would you like to use? (Use arrow keys)
# Choose CSS and hit Enter

Get inside the project folder:

cd angular-http-observables

To create the live search module, we will be using Bootstrap’s UI components. Run below command to install bootstrap:

npm install bootstrap

Add the bootstrap.min.css path inside styles array inside the package.json file:

"styles": [
      "node_modules/bootstrap/dist/css/bootstrap.min.css",
      "src/styles.css"
]

Create Live Search Layout with Bootstrap

Create a live search module for the Angular Http observable demo by pasting the following code inside app.component.html file:

<div class="container">
    <form>
        <div class="form-group search-bar">
            <!-- Search -->
            <input class="form-control" placeholder="Search..." type="text">

            <!-- Progres -->
            <div class="loader">
                <div class="c-three-dots-loader"></div>
            </div>
        </div>

        <!-- Search Result -->
        <div class="list-group">
            <div class="list-group-item list-group-item-action">
                <div _ngcontent-ert-c0="" class="media"><img alt="..." class="mr-3"
                        src="https://restcountries.eu/data/cod.svg">
                    <div class="media-body">
                        <p class="mt-0">Congo (Democratic Republic of the)</p>
                    </div>
                </div>
            </div>
            <div class="list-group-item list-group-item-action">
                <div class="media"><img alt="..." class="mr-3" src="https://restcountries.eu/data/fin.svg">
                    <div class="media-body">
                        <p class="mt-0">Finland</p>
                    </div>
                </div>
            </div>
            <div class="list-group-item list-group-item-action">
                <div class="media"><img alt="..." class="mr-3" src="https://restcountries.eu/data/nru.svg">
                    <div class="media-body">
                        <p class="mt-0">Nauru</p>
                    </div>
                </div>
            </div>
        </div>
    </form>
</div>

Import HttpClientModule

HttpClient is Angular’s tool for interacting with a web server over HTTP. Make HttpClient accessible in the entire Angular app in just two simple steps.

Firstly, import it inside the AppModule. And, secondly add HttpClient in the imports array :

import { HttpClientModule } from "@angular/common/http";

@NgModule({
  declarations: [...],
  imports: [
    HttpClientModule
  ],
  providers: [...],
  bootstrap: [...]
})

export class AppModule { }

Handle Angular HTTP Service with Observable

Next, generate the app/shared/country.ts class with the following command:

export class Country {
    public name: string;
    public flag: string;
}

Then, import CountryService and also insert the Angular service in the providers array in the AppModule. It make the service available in the entire app.

import { CountryService } from './shared/county.service';

@NgModule({
  declarations: [...],
  imports: [...],
  providers: [CountryService],
  bootstrap: [...]
})

export class AppModule { }

Next, generate the app/shared/search.service.ts using the following command:

ng generate service shared/county

Add the following code in app/shared/search.service.ts.

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Country } from './country';
import { Observable, of } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable({
  providedIn: 'root'
})

export class CountryService {
  endpoint: string = "https://restcountries.eu/rest/v2/name/";

  constructor(private http: HttpClient) { }

  searchCountry(term: string): Observable<Country[]> {
    let url = `${this.endpoint}${term}`;
    if (!term.trim()) {
      return of([]);
    }
    return this.http.get<Country[]>(url)
      .pipe(
        catchError(this.handleError<Country[]>('countries', []))
      )
  }

  private handleError<T>(operation = 'operation', result?: T) {
    return (error: any): Observable<T> => {
      console.log(`failed: ${error.message}`);
      return of(result as T);
    };
  }

}

• In this Angular observable tutorial we starting with importing the observable from the rxjs library.
• We used the rest countries API https://restcountries.eu/rest/v2/name/{name} to fetch the countries list.
• Next, inject the HttpClient module in the constructor to make the HTTP GET request.
• Then, we bind the Observable with search(term: string) method. It takes a string, basically entered by the user and will return an observable in which every item in the observable is Country[] list type.
• To handle the error, we declared a handleError function, and we added error handling mechanism with the rxjs pipe operator.

Managing HTTP Response with Observable and RxJS Operators

To handle the HTTP response via observable we will be using following RxJS operators.

Next, add the following code inside the app/app.component.ts:

import { Component, OnInit } from '@angular/core';
import { CountryService } from './shared/county.service';
import { Country } from './shared/country';
import { Observable, Subject } from 'rxjs';

import {
  tap,
  switchMap,
  debounceTime,
  distinctUntilChanged
} from "rxjs/operators";

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

export class AppComponent implements OnInit {
  loading: boolean = false;
  countries$: Observable<Country[]>;
  private searchTerms = new Subject<string>();

  constructor(private countryService: CountryService) { }

  search(term: string) {
    this.searchTerms.next(term);
  }

  ngOnInit(): void {
    this.countries$ = this.searchTerms.pipe(
      tap(_ => this.loading = true),
      debounceTime(300),
      distinctUntilChanged(),
      switchMap((term: string) => this.countryService.searchCountry(term)),
      tap(_ => this.loading = false)
    )
  }

}

• Define the countries$ observable and mapped it with Observable;
• Inject the CountryService inside the constructor.
• Set RxJS new Subject() with serachTerms private variable. It will emit the latest value entered by the user incorporating with search(term: string) { } method in the live country search module.
• Now, bind the countries$ variable with the searchTerms Subject along with RxJS pipeable operator. Inside this perform, the side effect with tap method here we are setting showing the loader, especially when the user enters any value.
• Next, we are setting the delay for 300ms after that call the distinctUntilChanged() method. Next, take the latest value by using the swithcMap() operator and call the searchCountry method in it and passed the latest value in it.
• When the request is called, and response is returned, then make the loader hidden by setting it up to false.

Display Data with Angular Async Pipe

Add the following code inside the app/app.component.html:

<div class="container">
  <form>
    <div class="form-group search-bar">
      <!-- Search -->
      <input type="text" class="form-control" placeholder="Search..." #searchBox (input)="search(searchBox.value)">

      <!-- Progres -->
      <div class="loader" *ngIf="loading">
        <div class="c-three-dots-loader"></div>
      </div>
    </div>

    <!-- Search Result -->
    <div class="list-group">
      <div class="list-group-item list-group-item-action" *ngFor="let country of countries$ | async">
        <div class="media">
          <img src="{{country.flag}}" class="mr-3" alt="...">
          <div class="media-body">
            <p class="mt-0">{{ country.name }}</p>
          </div>
        </div>
      </div>
    </div>
  </form>
</div>

Lastly, we are going to display the data using the Async pipe. Let’s understand a little bit about the async pipe.

The async pipe subscribes to an Observable or Promise and gets the most recent value it has released. Async pipe signifies the component to be examined for the latest emitted value. The benefit of the Async pipe is that it unsubscribes the observable and provides memory leakage protection when the component is destroyed.

Conclusion

Finally, we have completed the Angular 8 Observables tutorial with a live country search module example. In this tutorial, we got started with a primary objective: Handling Angular HTTP response with Observables, i hope you learned a lot from this tutorial.

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