How to Make an API Call in Angular? Create, Read, Update, and Delete Seamlessly

How to Make an API Call in Angular?

You want your Angular app to fetch data in real time and respond quickly to user requests. This goal involves setting up a well-structured environment and following reliable steps to handle all operations. When you build everything from the ground up, you ensure that every call works smoothly and meets your application’s requirements.

Below is a clear workflow for preparing Angular for HTTP activities. You will install and verify core tools, add the correct modules, and write a dedicated service. You will also review a sample GET request and learn about error handling and unsubscription methods.

Let’s get started with the basics - setting up the Angular environment. 

Set Up the Angular Environment

You need a consistent foundation for managing your project. This includes installing Node.js, the Angular CLI, and starting a new application folder.

Below are the clear steps:

Step 1: Confirm Node.js Installation

In your terminal or command prompt, type this command:

node -v

This command prints the installed Node.js version. 

Alternatively, you can also run the command listed below to see the version of NPM:

npm -v

You must have these tools properly installed to move forward.

Step 2: Install Angular CLI

You need Angular’s command-line tool for project creation. 

Run this command:

npm install -g @angular/cli

This command sets up the CLI globally, so you can access it from any folder on your machine.

Also Read: How to Install Angular CLI in Windows 10

Step 3: Create a New Angular Project

You can create a new folder with all the default Angular files by typing this command:

ng new my-app

When prompted, choose your routing or styling preferences. 

Once the process completes, enter the newly created directory using this command:

cd my-app

Now you have a clean workspace and can focus on the next step – importing HttpClientModule – without interruptions.

Also Read: How to Run the Angular Project [Step-By-Step Explanation]

Import and Configure HttpClientModule

You need Angular’s HttpClient features to send requests to an external API. By default, Angular sets up essential modules, but you still must add HttpClientModule in the main module file.

Below is a simple approach:

Step 1: Open app.module.ts

Locate this file in the src/app folder. This file declares the root module.

Step 2: Add HttpClientModule

Insert the following lines:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpClientModule } from '@angular/common/http';
import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
    // other components...
  ],
  imports: [
    BrowserModule,
    HttpClientModule // Import HttpClientModule here
    // other modules...
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

This code enables HTTP services in your application.

Step 3: Confirm Functionality

You can run the command listed below:

ng serve

Visit the link the command provides (often http://localhost:4200) to ensure the project compiles without errors.

Create a Dedicated Service for API Calls

API calls are usually kept in a separate service to keep the component logic simple. Below are the steps that’ll help you accomplish this requirement.

Step 1: Generate the Service

Type and Enter this command:

ng generate service api

This command creates two files: api.service.ts and api.service.spec.ts. You will work with the .ts file.

Step 2: Inject HttpClient

Open api.service.ts and add the following script:

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class ApiService {
  constructor(private http: HttpClient) {}

  // You can add methods here
}

In this snippet, HttpClient becomes accessible via this.http.

Step 3: Define Common Methods

You might need GET, POST, PUT, or DELETE. 

Here is an example:

getItems(): Observable<any> {
  return this.http.get('https://api.example.com/items');
}

postItem(payload: any): Observable<any> {
  return this.http.post('https://api.example.com/items', payload);
}

These return Observables, which means the data arrives asynchronously. You subscribe to the component to process it.

Also Read: HTTP Get Method and Post Method

Make an Example GET Call

You want to see an actual request that grabs information from a remote endpoint. Let’s assume you already defined a getData() method in your service. 

Below is a walk-through:

Step 1: Write the GET Method 

You have to write the GET method in api.service.ts. 

Here’s a sample example:

getData(): Observable<any> {
  return this.http.get('https://api.example.com/data');
}

Step 2: Call This Method in a Component

Go to a component (for example, app.component.ts). 

Here’s a sample example:

import { Component, OnInit } from '@angular/core';
import { ApiService } from '../api.service';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html'
})
export class AppComponent implements OnInit {
  data: any;

  constructor(private apiService: ApiService) {}

  ngOnInit() {
    this.apiService.getData().subscribe({
      next: (response) => {
        this.data = response;
        console.log('Fetched data:', this.data);
      },
      error: (err) => {
        console.error('Error fetching data:', err);
      }
    });
  }
}

Step 3: Observe the Output

Run this command in your console:

ng serve

When you open the browser at the provided address, check the console to see something like this:

Fetched data: {
  "results": [...]
}

Handling Errors and Unsubscribing

You can improve your code with additional checks that prevent your app from crashing. 

Here are the main considerations:

Step 1: Apply RxJS catchError

In your service, you intercept errors when something fails. 

Here’s an example:

import { catchError, throwError } from 'rxjs';

getData(): Observable<any> {
  return this.http.get('https://api.example.com/data').pipe(
    catchError(error => {
      console.error('Error occurred:', error);
      return throwError(() => error);
    })
  );
}

This snippet logs the error and returns a new error observable. You can handle it in your component or in a global interceptor.

Step 2: Unsubscribe in Components

If you subscribe manually, you should stop the subscription when the component unloads. A typical approach is to store the subscription in a variable and then unsubscribe in ngOnDestroy.

Here’s a sample example:

export class AppComponent implements OnInit, OnDestroy {
  private sub: Subscription | undefined;

  ngOnInit() {
    this.sub = this.apiService.getData().subscribe(response => {
      // handle response
    });
  }

  ngOnDestroy() {
    if (this.sub) {
      this.sub.unsubscribe();
    }
  }
}

In a simpler setup, you can use the async pipe in your template, which manages subscriptions for you.

Step 3: Confirm the Output

Run this command:

ng serve

If an error occurs (like a bad URL), the console might show something like this:

Error occurred: HttpErrorResponse { ... }

This confirmation means your error handling is working.

By following these steps, you lay the groundwork for stable and efficient API calls in Angular. You can adapt the methods above to suit your needs, such as chaining multiple calls or handling more specific response types.

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How to Call REST API in Angular?

Suppose you have an Angular project that needs to talk to a remote server. This section shows how to represent data using TypeScript interfaces, carry out basic and advanced operations (CRUD), and apply important features like interceptors. By working through this material, you will see exactly how to create and organize every call that interacts with a REST API.

These steps will guide you from basic setups to advanced techniques, with examples that can fit many different applications.

Define Interfaces for Type Safety

You need a strong method for keeping data accurate in Angular projects. When you fetch or post objects, it helps to structure them in a way that reduces mistakes and boosts maintainability. That is where TypeScript interfaces come into play.

Here is how you can apply clear steps to define and use interfaces:

Step 1: Create an Interface File

In your src/app/models folder (or any logical folder), you can run this command:

ng generate interface models/user

This command makes a file called user.ts inside models. You can also create the file manually.

Step 2: Define the Fields

Open user.ts and write this command:

export interface User {
  id: number;
  name: string;
  email: string;
}

This code describes what a User object contains.

Step 3: Reference the Interface

In a service or component, you might use this command:

import { User } from './models/user'; // or your path

getUsers(): Observable<User[]> {
  return this.http.get<User[]>('https://api.example.com/users');
}

This approach ensures that your incoming data lines up with the expected fields. If something is off, you will see errors at compile time.

Demonstrate CRUD Operations

You often need four main actions: create, read, update, and delete. These actions, called CRUD, let you manage resources in your application. Each operation involves a different HTTP method but follows a similar pattern.

Below are steps that explain the basic CRUD setup:

Step 1: Create a GET Method

Inside your service (for instance, api.service.ts), you may write this command:

import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import { User } from './models/user';

export class ApiService {
  constructor(private http: HttpClient) {}

  getUsers(): Observable<User[]> {
    return this.http.get<User[]>('https://api.example.com/users');
  }
}

This method retrieves a list of users from the server.

Step 2: Build a POST Method

If you need to add a user to your database, use this command:
addUser(payload: User): Observable<User> {
  return this.http.post<User>('https://api.example.com/users', payload);
}

This code sends a new User object to the server and expects the created object in response.

Step 3: Include a PUT Method

For updating an existing user, add this command:

If you need to add a user to your database, use this command:
addUser(payload: User): Observable<User> {
  return this.http.post<User>('https://api.example.com/users', payload);
}

This call modifies fields of a user identified by userId.

Step 4: Finalize with DELETE

To remove a user, add this command:

deleteUser(userId: number): Observable<any> {
  return this.http.delete(`https://api.example.com/users/${userId}`);
}

You usually receive a status or confirmation once the operation completes.

Step 5: Use Components to Call These Methods

A component typically subscribes to these methods and handles what to do next (for example, displaying data or refreshing a list). 

Here’s a sample example:

ngOnInit() {
  this.apiService.getUsers().subscribe({
    next: (users) => {
      this.usersList = users;
    },
    error: (err) => {
      console.error('Unable to load users:', err);
    }
  });
}

This code is part of a practical flow: the service manages the logic, and the component updates the interface.

Also Read: Understanding CRUD Operations in ASP.NET MVC

Use Interceptors for Authentication and Error Handling

You may want to attach tokens to your requests or deal with specific errors in a unified way. Angular interceptors let you intercept an outgoing request or an incoming response.

Below are steps that help you set up a custom interceptor:

Step 1: Create an Interceptor File

You can run this command:

ng generate interceptor auth

This command creates an auth.interceptor.ts file where you can inject logic into every request.

Step 2: Implement the Interceptor

Open auth.interceptor.ts and write this command:

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const token = 'Bearer token123';
    const clonedRequest = req.clone({
      setHeaders: { Authorization: token }
    });
    return next.handle(clonedRequest);
  }
}

This code appends an Authorization header to every request.

Step 3: Register the Interceptor

In your app.module.ts, add this command:

import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { AuthInterceptor } from './auth.interceptor';

@NgModule({
  ...
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthInterceptor,
      multi: true
    }
  ],
  ...
})
export class AppModule {}

By setting multi to true, you allow multiple interceptors in the future.

Key Differences Between HttpClient and HttpBackend

You might see references to HttpBackend in Angular. HttpClient and HttpBackend serve different purposes. 

Here are the key differences between the two:

Also Read: How to Open a JSON File? A Complete Guide to Creating and Managing JSON Files

Handling CORS

When your Angular app and the server run on different domains, you usually need Cross-Origin Resource Sharing (CORS). Without it, browsers may block requests. Fortunately, Angular itself does not require a special setup, but the server must allow the request from your Angular domain.

Below is a typical approach:

Step 1: Confirm Server Headers

On the server side, set this:

Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, PUT, DELETE
Access-Control-Allow-Headers: Content-Type, Authorization

This snippet is placed in the server’s response headers.

Step 2: Test Calls

Use a tool like Postman or your Angular front end. If everything is correct, the browser will no longer block the request.

How to Handle Multiple API Calls in Angular?

You may have several endpoints that need to run at once, or you might prefer an ordered approach that only runs a second call when the first one finishes. Either way, you should know how to handle these different data-fetching patterns. Your Angular app can handle multiple calls effectively if you set up the right strategy.

In this section, you will see how to execute calls one by one or all at once. You will learn where each style works best and how to apply practical techniques like forkJoin or Promise.all. 

Sequential vs Parallel API Calls

You have two core approaches when dealing with several endpoints. You can either wait for one call to finish before starting the next or run them all together. Each style affects the speed of your app and the complexity of your code.

Here are a few key points to make things clear:

• Sequential Calls: The next request only starts after the previous request completes. This approach ensures you handle responses in a set order. However, it can increase the total time if you have many calls. For example, if each call takes 2 seconds and you run 5 calls in a row, you might wait 10 seconds overall.
• Parallel Calls: Multiple requests go out at the same time. You do not wait for one to complete before launching the next, so you often save time. You can handle the results as soon as they all arrive. You do need to be mindful of how you handle success or failure if any call fails, but this style typically boosts performance.

How to Make Parallel Calls in Angular with forkJoin?

You can make simultaneous calls more cleanly in Angular using forkJoin. This method waits for all included observables to finish, then produces a result that includes everything at once.

Below is a step-by-step outline:

Step 1: Import forkJoin

Open your TypeScript file that contains the logic for parallel calls. At the top, add this command:

import { forkJoin } from 'rxjs';
import { HttpClient } from '@angular/common/http';

This code ensures you can use forkJoin and the HTTP methods.

Step 2: Specify Your Requests

Suppose you need user data and cart data. Write this command:

constructor(private http: HttpClient) {}

getData() {
  forkJoin({
    user: this.http.get('https://api.example.com/user/1'),
    cart: this.http.get('https://api.example.com/user/1/cart')
  }).subscribe({
    next: (data: any) => {
      console.log('User Data:', data.user);
      console.log('Cart Data:', data.cart);
    },
    error: (err) => {
      console.error('Error in parallel calls:', err);
    }
  });
}

You pass an object containing the observables. forkJoin then runs them together.

Step 3: Confirm the Output

You can run your Angular app with this command:

ng sarve

Then look at your browser console. You might see something like this:

User Data: { "id": 1, "name": "Alice" }
Cart Data: { "items": [...], "total": 199.99 }

That indicates both requests completed, and each returned the relevant data.

Using Promise.all or Promise.allSettled (JavaScript)

If you work outside Angular’s HttpClient or want to mix fetch or other promise-based calls, you can handle multiple operations with native JavaScript functions. These functions operate similarly but have unique aspects.

Here are the main steps to apply them:

Step 1: Write Your Promises

Suppose you rely on the standard fetch API. You might have this:

const promiseA = fetch('https://jsonplaceholder.typicode.com/posts/1');
const promiseB = fetch('https://jsonplaceholder.typicode.com/posts/2');

Each fetch request returns a promise.

Step 2: Parallel Execution with Promise.all

You run them together by placing them in an array:

async function getMultiplePosts() {
  try {
    const responses = await Promise.all([promiseA, promiseB]);
    console.log('All responses resolved:', responses);
  } catch(err) {
    console.error('One or more requests failed:', err);
  }
}

Promise.all waits until every promise succeeds or is rejected. If one promise is rejected, the entire call fails.

Step 3: Consider Promise.allSettled

If you want to handle any success or failure individually, here’s what you can do:

async function getAllOrNone() {
  const outcome = await Promise.allSettled([promiseA, promiseB]);
  outcome.forEach((result) => {
    if (result.status === 'fulfilled') {
      console.log('Fulfilled:', result.value);
    } else {
      console.log('Rejected:', result.reason);
    }
  });
}

This variant does not stop if one call fails. It returns an array of outcomes that indicate each success or failure.

Also Read: Understanding JavaScript Promises

Practical Considerations While Making Multiple API Calls

Your choice between sequential or parallel depends on whether the tasks depend on each other’s results and how quickly you want data. 

Here are the key considerations:

• Independent Data Sources: If you need multiple details that do not rely on each other, it is more efficient to send calls in parallel. For instance, you can fetch user info and product listings at the same time.
• Chained Results: If you must feed the response of one call into the next, you need a sequential flow. This ensures you do not start the second call before you have the data from the first.
• Network Load: If you have too many simultaneous requests, you may overwhelm the network or the backend. Combining or batching requests can be more efficient than sending them separately if the payload fits within reasonable limits.

When you handle multiple calls in a single operation, you avoid unnecessary waiting times. Whether you use Angular’s forkJoin, Promise.all, or standard sequential code, you make each data retrieval step predictable and transparent to you and your teammates.

What Are Best Practices for Making Efficient API Calls in Angular?

When you want to improve performance and maintain clean code, you should structure your API calls in a way that avoids repeated logic and unnecessary fetches. This approach keeps users happy, reduces server load, and keeps your code organized. You will see that a few targeted tactics can greatly boost speed and stability.

Below, you will discover several methods that expand your existing Angular skills. 

1. Centralizing Logic in Services

You can simplify your entire codebase by keeping all HTTP calls in dedicated services. This practice also helps you modify endpoints or credentials in one place.

Below is a clear breakdown:

Step 1: Create a Single Source of Truth

Generate a file like api.service.ts. In there, write methods such as:

export class ApiService {
  constructor(private http: HttpClient) {}

  getData(endpoint: string): Observable<any> {
    return this.http.get(endpoint);
  }

  updateData(endpoint: string, body: any): Observable<any> {
    return this.http.put(endpoint, body);
  }
}

Step 2: Inject Services in Components: 

Anywhere you need data, bring in the service:

constructor(private apiService: ApiService) {}

ngOnInit() {
  this.apiService.getData('https://example.com/items').subscribe({
    next: (res) => console.log('Items:', res),
    error: (err) => console.error('Error:', err)
  });
}

You keep components free of direct HTTP logic, which makes them easier to read.

Step 3: Verify Uniform Patterns

By checking only the service file, you confirm that all data-fetch rules and transformations remain consistent throughout your app.

2. Implementing Caching and Pagination

Even small datasets can slow down your app if fetched repeatedly. To keep load times in check, you can store certain responses locally or request data in chunks.

Below are some steps to handle this efficiently:

Step 1: Cache Frequently Used Data 

For example, you can store results in memory or localStorage. 

In api.service.ts, you might do this:

private cache: any = {};

getCachedData(url: string): Observable<any> {
  if (this.cache[url]) {
    return of(this.cache[url]);
  } else {
    return this.http.get(url).pipe(
      tap(data => this.cache[url] = data)
    );
  }
}

This code checks if cache[url] exists. If it does, it returns the result immediately.

Step 2: Use Pagination and Filtering

When data is large, you do not want to fetch everything at once. Instead, send queries like this:

this.http.get(`https://api.example.com/items?page=${page}&limit=20`);

This retrieves manageable slices. Users see quick loads, and you conserve resources.

Also Read: How to Implement Pagination in AngularJS – Easy Guide

Step 3: Confirm Storage Integrity

Test by changing pages or filtering criteria. Ensure that your local or memory-based caching only applies when relevant. If data becomes stale, you might need to refresh it periodically.

3. Error Handling Patterns

You can catch issues on multiple levels: in a global interceptor, within services, or inside components. A flexible setup usually involves combining them so you do not miss errors.

Let us look at some recommended steps:

Step 1: Use a Global Interceptor 

Set up a file like error.interceptor.ts:

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).pipe(
      catchError(error => {
        console.error('Global error:', error);
        return throwError(() => error);
      })
    );
  }
}

This logs every HTTP-related failure in one place.

Step 2: Add Local catchError

If your operation needs a unique reaction, you can do it in the service:

this.http.post('https://api.example.com/items', item).pipe(
  catchError(err => {
    console.error('Item save failed:', err);
    return throwError(() => err);
  })
);

This method ensures that you can override the default approach when required.

Step 3: Choose Where to Handle

By default, errors bubble up. You can either display an alert from the component or rely on a global UI message. Ensure your logic is consistent across the application.

4. Using the Async Pipe

Subscriptions and unsubscriptions add to your code’s complexity. Angular’s async pipe helps you manage Observables directly in your templates.

Take a look at the steps:

Step 1: Return an Observable from the Service

Type this command in api.service.ts:

getUsers(): Observable<User[]> {
  return this.http.get<User[]>('https://api.example.com/users');
}

Step 2: Bind the Observable in the Component

Instead of subscribing manually, store it in a property:

userList$ = this.apiService.getUsers();

This variable holds an Observable of the data, not the data itself.

Step 3: Use the Async Pipe in the Template

Type this command in app.component.html:

<div *ngIf="userList$ | async as users">
  <ul>
    <li *ngFor="let user of users">
      {{ user.name }}
    </li>
  </ul>
</div>

Angular subscribes automatically. When you leave the page, it unsubscribes. This prevents leaks and lowers overhead.

5. Security Considerations

You want to protect your connections and any sensitive details. Failing to secure these areas could lead to unauthorized data access or harmful modifications.

Here are the key security considerations you must follow when making an API call in Angular:

• Always Use HTTPS: Make sure your URLs start with https. This encrypts data in transit, so attackers cannot see or change it. Your server needs an SSL certificate that browsers trust.
• Secure Token Storage: If you handle tokens, keep them out of global variables. Instead, store them in HttpOnly cookies or in a secure location. For instance, you might store a short-lived token in memory and refresh it with a silent re-auth flow.
• Consider Standard Approaches: Many developers rely on JSON Web Tokens (JWT) or OAuth for verifying user identity. You can place the token in an interceptor:

intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
  const authReq = req.clone({
    setHeaders: {
      Authorization: `Bearer ${this.getToken()}`
    }
  });
  return next.handle(authReq);
}

This snippet ensures your calls remain protected. Make sure the token is valid and that your backend checks authenticity properly.

Applying these recommendations — services, caching, robust error handling, the async pipe, and secure connections — will reduce unnecessary overhead, maintain strong organization, and keep user data safe.

Also Read: JavaScript Async Await

How Do You Manage Errors and Interceptors in Angular?

You want your Angular application to handle problems without disrupting the user experience. A well-structured approach allows you to catch common errors in one place yet still customize how you respond in specific areas. You also need an efficient way to show feedback, such as loaders or spinners, whenever calls are in progress.

This section explains how to set up a global interceptor that logs errors or displays friendly messages. It also covers local handling techniques that allow you to address unique scenarios.

Creating a Global Error Interceptor

Sometimes, you need a shared place to detect any issue that arises across all your Angular HTTP calls. A global interceptor helps you apply consistent policies so you do not have to duplicate logic in every service or component.

Below is a detailed outline:

Step 1: Generate the Interceptor File

You can type this command:

ng generate interceptor error

This command creates a file, for example error.interceptor.ts, which is where you store the logic.

Step 2: Implement the Interceptor Class

Open error.interceptor.ts and add this command: 

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).pipe(
      catchError(err => {
        console.error('Global error caught:', err);
        // You can show a toast, redirect the user, or perform other actions here
        return throwError(() => err);
      })
    );
  }
}

This code detects errors on every request and logs them or handles them as needed.

Step 3: Register the Interceptor

To make it active, open your app.module.ts and type this command:

import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { ErrorInterceptor } from './error.interceptor';

@NgModule({
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: ErrorInterceptor,
      multi: true
    }
  ],
  ...
})
export class AppModule {}

The multi: true property means you can add more interceptors in the future without losing the functionality of this one.

When you run the command listed below, every HTTP request will pass through this interceptor:

ng serve

If an error occurs (like a 404 or server timeout), you will see the global message in your console or any special UI element you choose.

Local Error Handling with catchError

You might need more specific error management for certain parts of your app. A global interceptor catches everything, but local handling helps you deliver targeted responses in some methods.

Consider these steps:

Step 1: Add a Method in Your Service

In a file such as user.service.ts, you might write this command:

import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { catchError, throwError } from 'rxjs';

createUser(user: any): Observable<any> {
  return this.http.post('https://api.example.com/users', user).pipe(
    catchError((error: HttpErrorResponse) => {
      console.error('Error creating user:', error);
      // Decide how to transform or forward the error
      return throwError(() => 'Failed to create user');
    })
  );
}

This snippet logs the issue and returns a more descriptive message that you can handle in your component.

Step 2: Subscribe in the Component

By capturing the error in the service, you can also respond at the component level if you need to show an alert or modify the UI:

this.userService.createUser(this.newUser).subscribe({
  next: (data) => {
    console.log('User created:', data);
  },
  error: (err) => {
    console.error('Creation error:', err);
    // Possibly show a modal or in-page alert here
  }
});

You see how the error message 'Failed to create user' from the service is accessible in err.

Step 3: Confirm Your Flows

Test with valid and invalid data. For instance, run this command and try an erroneous request:

ng serve

If the endpoint is down or you have a wrong URL, you see the console output or a UI notification about the failure.

Handling Loader States

Beyond errors, you want to give users visual cues that the app is working. This helps them avoid thinking the interface has frozen when a long call is in progress.

Here’s how you can set up a loader:

Step 1: Create a Service to Track State

You can run this command:

ng generate service loader

This command generates loader.service.ts. 

Inside, you can keep a BehaviorSubject that toggles loading on or off:

import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class LoaderService {
  public isLoading = new BehaviorSubject<boolean>(false);

  showLoader() {
    this.isLoading.next(true);
  }

  hideLoader() {
    this.isLoading.next(false);
  }
}

Step 2: Activate in an Interceptor or Before/After Calls

One option is to add it to an interceptor:

import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';
import { finalize } from 'rxjs/operators';
import { LoaderService } from './loader.service';

@Injectable()
export class LoaderInterceptor implements HttpInterceptor {
  constructor(private loaderService: LoaderService) {}

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    this.loaderService.showLoader();
    return next.handle(req).pipe(
      finalize(() => {
        this.loaderService.hideLoader();
      })
    );
  }
}

This code calls showLoader() when a request begins, then calls hideLoader() once everything finishes.

Step 3: Present the Loader in Your Templates

Suppose you have a component named app-loader that includes a spinner. You can bind it to LoaderService.isLoading:

<div *ngIf="loaderService.isLoading | async" class="loader-overlay">
  <div class="loader"></div>
</div>

Whenever the observable emits true, the loader appears; when it emits false, the loader disappears.

By combining a global interceptor for broad oversight, local catchError for method-specific issues, and a loader indicator for in-progress requests, you deliver a more polished and predictable experience to every user.

Key Takeaways You Must Remember When Calling an API

You have explored detailed methods for setting up Angular to communicate with external data. It is wise to keep a concise list of reminders to maintain speed and consistency in your application. These pointers also help you avoid common mistakes and keep your architecture flexible.

Below is a short set of guidelines that highlight important elements of well-organized API calls:

• Import HttpClientModule: Add this module in your app.module.ts to activate Angular’s HTTP features throughout the project.
• Keep Services Modular: Place your endpoints and request logic in dedicated files to prevent code duplication and allow easy maintenance.
• Use Typed Interfaces: Define clear interfaces, like User or Product, so Angular enforces consistency and catches errors at build time.
• Rely on Interceptors: Manage authentication headers, logging tasks, or general error handling from a single spot in your application.
• Consider Parallel Calls: Use strategies such as forkJoin or Promise.all when you need multiple independent datasets at once, which improves performance.

Conclusion

Now that you have seen each detail of building efficient Angular API calls, you can create apps that handle data with speed and reliability. Each technique you apply — typed interfaces, concurrency, error handling, and security — contributes to a smooth user experience.

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