Skip to main content

Angular Application To Consume GraphQL Endpoint Using Apollo Angular Library

In this article, we will learn about consuming GraphQL API from angular applications using the Apollo Angular library.

Overview On GraphQL API:

As a front-end developer, no need to understand about in-depth nature of the GraphQL API. But it will be good to know about few key features about it for development.

GraphQL API mostly has a single endpoint. So data fetching or updating will be carried out by that single endpoint. For posting data or querying data, we have to follow its own syntax. GraphQL carries two important operations:
  • Query - fetching data
  • Mutation - updating or saving data.

Create A Sample Angular Application:

Let's create a sample angular application where we are going to implement techniques to consume the GraphQL endpoint.
Command To Install Angular CLI:(If not installed on your system previously)
npm install -g @angular/cli
Angular CLI Command To Create Angular App:
ng new your_project_name
Command To Run App:
ng serve

Install Apollo Angular Library:

Apollo Angular provides us an easy way to install and configure it into our application with a simple 'ng' command below.
Command To Install And Setup Apollo Angular :
ng add apollo-angular
The command installs 3 different libraries like 'apollo-angular', '@apollo/client', 'graphql'.
The 'graphql.module.ts' a new file will be created with all startup configurations regarding GraphQL.

Configure GraphQL Endpoint:

For this demo, I have developed a sample GraphQL endpoint that I will use in our angular sample application.

In the 'graphql.module.ts' file constant variable 'uri', we need to assign our GraphQL endpoint value.
src/app/graphql.module.ts:

GraphQL Query Syntax:

In GraphQL, the Query represents the fetching of the data. The sample syntax of the query looks as below.
Query Syntax:
query{
  MyGadgets{
    Id,
    ProductName,
    Brand
  }
}
  • 'query' keyword to understand the request type.
  • 'MyGadgets' will be the method name on the server.
  • The 'Id', 'ProductName', 'Brand' are properties to be returned in the response data. The beauty of GraphQL is to fetch only required props. For suppose if we need only 'ProductName' then we can pass only that property in the request so that response will contain only 'ProductName'.

Consume Basic Query:

The above tool(generated by the server application) is very helpful to test the GraphQL endpoint by all the developers. From the pic, we can see the GraphQL query and response. Now here we are going to prepare the same query in our angular application and then invoke the endpoint and then capture the response.

Let's create an interface type for the response model. So let's create a folder like 'models' and then add a file like 'gadget.ts'
models/gadget.ts:
export interface Gadget {
    Id:number,
    ProductName:string,
    Brand:string,
    Cost:number,
    Type:string
}
Now update our 'app.component.ts' with the following logic.
src/app/app.componen.ts:
import { Component, OnInit } from '@angular/core';
import {gql, Apollo} from 'apollo-angular';
import { Gadget } from './models/gadget';

const Get_MyGadgets = gql`
query{
  MyGadgets{
    Id,
    ProductName,
    Brand,
  }
}
`;

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  allGadets:Gadget[] = [];
  constructor(private apollo: Apollo){}
  ngOnInit(): void {
    this.apollo.watchQuery<any>({
      query: Get_MyGadgets
    })
    .valueChanges
    .subscribe(({data, loading}) => {
      console.log(loading);
      this.allGadets = data.MyGadgets;
    })
  }
}
  • (Line 2) Importing few instances from the 'apollo-angular' library.
  • (Line: 5-13) Assigned our query as a constant value. We have prefixed 'gql' to our query, 'gql' parse our string GraphQL query to the GraphQL document.
  • (Line: 22) Injecting 'Apollo' constructor.
  • (Line: 24-31) Invoking GraphQL endpoint and subscribing to the response. The 'watchQuery' method from the 'Apollo' instance returns 'valueChanges' which is observable. To capture the response data we have to subscribe to it. Subscriber reads object that contains properties like 'data' and 'loading'. The 'data' property contains responses from the GraphQL server. The 'loading' property returns a boolean value to represent the completion of the API call.
Now we have to bind our response data.
src/app/app.component.html:
<table class="table table-dark table-striped">
  <thead>
    <tr>
      <th scope="col">Id</th>
      <th scope="col">Product Name</th>
      <th scope="col">Brand</th>
      <th scope="col">Cost</th>
      <th scope="col">Type</th>
    </tr>
  </thead>
  <tbody>
    <tr *ngFor="let gadget of allGadets">
      <td>{{gadget.Id}}</td>
      <td>{{gadget.ProductName}}</td>
      <td>{{gadget.Brand}}</td>
      <td>{{gadget.Cost}}</td>
      <td>{{gadget.Type}}</td>
    </tr>
  </tbody>
</table>
One final step is to import the 'FormModule' from '@angular/form' into the 'app.module.ts'.

Now start the application and checks the output of our sample.

Filters In GraphQL Query:

We can have filters in GraphQL Query. The filters are nothing but the query params or user payload.
Query Syntax:
query ($brandName:String){
  BrandFilter(brand:$brandName){
    Id,
    ProductName,
    Brand
  }
}
Variable Syntax: 
{
  "brandName":"Samsung"
}
Usually, query parameters or payload is dynamic data passed by the users. So appropriate way to pass the query data into GraphQL query is to use GraphQL Variables. In 'Variable' object property name 'brandName' should match with '$brandName' in the GraphQL Query. The ($bradName:String) means defining the type for the variable. The 'brand' is the input parameter for the 'BrandFilter' function inside of the server. So to pass the variable data we will assign '$brandName' to 'brand' in 'BrandFilter'.

Consume Query With Filters:

Upgrade our sample application to use a GraphQL Query with filter data. So that we will create a search bar where we will filter data by the gadget's brand name.
src/app/app.component.ts:
import { Component, OnInit } from '@angular/core';
import {gql, Apollo} from 'apollo-angular';
import { Gadget } from './models/gadget';

const Get_BrandFilter = gql`
query ($brand:String){
  BrandFilter(brand:$brand){
    Id,
    ProductName,
    Brand
  }
}`;

// Some code hidden for display purpose

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

  searchByBrand(){
   this.apollo.watchQuery<any>({
      query: Get_BrandFilter,
      variables:{
        brand: this.selectedBrand
      }
    })
    .valueChanges
    .subscribe(({data, loading}) => {
      console.log(loading);
      this.allGadets = data.BrandFilter;
    });
  }
}
  • (Line: 5-12) GraphQL Query with filtering capability had declared as a constant.
  • (Line: 23) The 'selectedBrand' variable will be used to store the user-entered brand name to filter the data.
  • (Line: 26-38) The 'searchByBrand' method to invoke GraphQL endpoint with the filtered data. Here we can observe user-entered data passed to the 'variables' object.
Now on top of our Html table, we will add a small form that contains a textbox to search the data by the brand name.
src/app/app.component.ts:
<form class="row g-3">
  <div class="col-auto">
    <label for="txtSearch" class="visually-hidden">Search By Brand</label>
    <input type="text" [(ngModel)]="selectedBrand" name="txtSearch" class="form-control" id="txtSearch" placeholder="Search By Brand">
  </div>
  <div class="col-auto">
    <button type="submit" class="btn btn-primary mb-3" (click)="searchByBrand()">Search</button>
  </div>
</form>
  • (Line: 4) Text field enabled model binding where we are going to capture the data entered into the 'selectedBrand' variable.
  • (Line: 7) Button click event register with method 'searchByBrand'.
Now run the application and filter some data by brand name and check the output.

GraphQL Mutation:

The mutation is meant to change the state of the data like creating or updating a record.
Mutation Syntax:
mutation ($inputType:GadgetsInput ){
 Save(gadgetInput:$inputType) {
    Id,
    ProductName,
    Brand,
    Cost,
    Type
 }
}
Variable Syntax: 
{
   "inputType":{
   "ProductName":"Think Pad 2.0",
   "Brand":"Samsung",
   "Cost":7500,
   "Type": "Laptop"
  }
}
  • The 'mutation' keyword determines GraphQL type.
  • The '$inputType' name should match with the 'variable' parent object property name like 'inputType'.
  • The '$inputType' type is defined as 'GadgetsInput' this name should match with the server-side class name.
  • The 'Save' method is the sever method where it contains logic to add a new record to the database.
  • We have defined properties to be returned as the response to the newly created object. In the sample above we are requesting all the properties of the newly created record.

Consume Mutation:

Now from our sample, we are going to invoke GraphL Mutation to create a new record.
src/app/app.component.ts:
import { Component, OnInit } from '@angular/core';
import {gql, Apollo} from 'apollo-angular';
import { Gadget } from './models/gadget';

// some existing code hidden for display purpose
const Post_Save = gql
`mutation ($inputType:GadgetsInput ){
  Save(gadgetInput:$inputType) {
     Id,
     ProductName,
     Brand,
     Cost,
     Type
  }
 }`  

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  allGadets:Gadget[] = [];
  selectedBrand:string = '';
  gadgetForms = {
    Brand:'',
    Cost:0,
    ProductName:'',
    Type:''
  };
  newGadget(){
    this.apollo.mutate({
      mutation:Post_Save,
      variables:{
        inputType:{
          ProductName: this.gadgetForms.ProductName,
          Brand: this.gadgetForms.Brand,
          Cost: Number(this.gadgetForms.Cost),
          Type: this.gadgetForms.Type
        }
      }
    }).subscribe(({data}) => {
      let gadgets = Object.assign([], this.allGadets)
      gadgets.unshift(data["Save"]);
      this.allGadets = gadgets;
    })
  }
}
  • (Line: 7-15) Mutation string constant
  • (Line: 25-30) The 'gadgetForms' object used for model binding of data from the form.
  • (Line: 31-47) GraphQL mutation call invoking. Here now we are using 'mutate' method from the 'Apollo' instance. We passing our 'Post_Save' constant value to the 'mutation' property. Inside of the 'variable' property we have created a property 'inputType' this should name must match with '$inputType' inside of 'Post_Save' constant. Our payload needs to be assigned to the 'inputType' property. On a successful response, we are updating the newly created record into our list and displaying it.
Now let's create a small form to creating new records.
src/app/app.component.html: 
<form class="row g-3">
  <div class="col-auto">
    <label for="txtProductName" class="visually-hidden">Product Name</label>
    <input type="text" class="form-control" [(ngModel)]="gadgetForms.ProductName" id="txtProductName" name="txtProductName" placeholder="Product Name">
  </div>
  <div class="col-auto">
    <label for="txtBrand" class="visually-hidden">Brand</label>
    <input type="text" class="form-control" [(ngModel)]="gadgetForms.Brand" id="txtBrand" name="txtBrand" placeholder="Brand">
  </div>
  <div class="col-auto">
    <label for="txtCost" class="visually-hidden">Cost</label>
    <input type="text" class="form-control" [(ngModel)]="gadgetForms.Cost" id="txtCost" name="txtCost" placeholder="Cost">
  </div>
  <div class="col-auto">
    <label for="txtType" class="visually-hidden">Type</label>
    <input type="text" class="form-control" [(ngModel)]="gadgetForms.Type" id="txtType" name="txtType" placeholder="Type">
  </div>
  <div class="col-auto">
    <button type="submit" class="btn btn-primary mb-3" (click)="newGadget()">Add</button>
  </div>
</form>
Now test our application by creating a new record.
So that's all about the small intro on Apollo Angular library to consume the GraphQL endpoint.

Video Session:

Support Me!
Buy Me A Coffee PayPal Me

Wrapping Up:

Hopefully, I think this article delivered some useful information on integrating the Apollo Angular library to consume GraphQL endpoint in Angular application. I love to have your feedback, suggestions, and better techniques in the comment section below.

Follow Me:

Labels:

Comments

  1. PratikApril 15, 2022 at 11:51 PM

    This was really helpful. I was actually looking for creating something similar though my output would be in the graph format. this provides me a great starting point. Bookmarked !

    ReplyDelete

Post a Comment

Popular posts from this blog

.NET6 Web API CRUD Operation With Entity Framework Core

In this article, we are going to do a small demo on AspNetCore 6 Web API CRUD operations. What Is Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, desktop apps. In simple terminology API(Application Programming Interface) means an interface module that contains a programming function that can be requested via HTTP calls to save or fetch the data for their respective clients. Some of the key characteristics of API: Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Supports default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. The ideal platform to build REST full services. Create A .NET6 Web API Application: Let's create a .Net6 Web API sample application to accomplish our
6 comments
Read more

Angular 14 Reactive Forms Example

In this article, we will explore the Angular(14) reactive forms with an example. Reactive Forms: Angular reactive forms support model-driven techniques to handle the form's input values. The reactive forms state is immutable, any form filed change creates a new state for the form. Reactive forms are built around observable streams, where form inputs and values are provided as streams of input values, which can be accessed synchronously. Some key notations that involve in reactive forms are like: FormControl - each input element in the form is 'FormControl'. The 'FormControl' tracks the value and validation status of form fields. FormGroup - Track the value and validate the state of the group of 'FormControl'. FormBuilder - Angular service which can be used to create the 'FormGroup' or FormControl instance quickly. Form Array - That can hold infinite form control, this helps to create dynamic forms. Create An Angular(14) Application: Let'
3 comments
Read more

Part-1 Angular JWT Authentication Using HTTP Only Cookie[Angular V13]

In this article, we are going to implement a sample angular application authentication using HTTP only cookie that contains a JWT token. HTTP Only JWT Cookie: In a SPA(Single Page Application) Authentication JWT token either can be stored in browser 'LocalStorage' or in 'Cookie'. Storing JWT token inside of the cookie then the cookie should be HTTP Only. The HTTP-Only cookie nature is that it will be only accessible by the server application. Client apps like javascript-based apps can't access the HTTP-Only cookie. So if we use authentication with HTTP only JWT cookie then we no need to implement custom logic like adding authorization header or storing token data, etc at our client application. Because once the user authenticated cookie will be automatically sent to the server by the browser on every API call. Authentication API: To implement JWT cookie authentication we need to set up an API. For that, I had created a mock authentication API(Using the NestJS Se
Post a Comment
Read more

Unit Testing Asp.NetCore Web API Using xUnit[.NET6]

In this article, we are going to write test cases to an Asp.NetCore Web API(.NET6) application using the xUnit. xUnit For .NET: The xUnit for .Net is a free, open-source, community-focused unit testing tool for .NET applications. By default .Net also provides a xUnit project template to implement test cases. Unit test cases build upon the 'AAA' formula that means 'Arrange', 'Act' and 'Assert' Arrange - Declaring variables, objects, instantiating mocks, etc. Act - Calling or invoking the method that needs to be tested. Assert - The assert ensures that code behaves as expected means yielding expected output. Create An API And Unit Test Projects: Let's create a .Net6 Web API and xUnit sample applications to accomplish our demo. We can use either Visual Studio 2022 or Visual Studio Code(using .NET CLI commands) to create any.Net6 application. For this demo, I'm using the 'Visual Studio Code'(using the .NET CLI command) editor. Create a fo
6 comments
Read more

A Small Guide On NestJS Queues

NestJS Application Queues helps to deal with application scaling and performance challenges. When To Use Queues?: API request that mostly involves in time taking operations like CPU bound operation, doing them synchronously which will result in thread blocking. So to avoid these issues, it is an appropriate way to make the CPU-bound operation separate background job.  In nestjs one of the best solutions for these kinds of tasks is to implement the Queues. For queueing mechanism in the nestjs application most recommended library is '@nestjs/bull'(Bull is nodejs queue library). The 'Bull' depends on Redis cache for data storage like a job. So in this queueing technique, we will create services like 'Producer' and 'Consumer'. The 'Producer' is used to push our jobs into the Redis stores. The consumer will read those jobs(eg: CPU Bound Operations) and process them. So by using this queues technique user requests processed very fastly because actually
7 comments
Read more

Angular 14 State Management CRUD Example With NgRx(14)

In this article, we are going to implement the Angular(14) state management CRUD example with NgRx(14) NgRx Store For State Management: In an angular application to share consistent data between multiple components, we use NgRx state management. Using NgRx state helps to avoid unwanted API calls, easy to maintain consistent data, etc. The main building blocks for the NgRx store are: Actions - NgRx actions represents event to trigger the reducers to save the data into the stores. Reducer - Reducer's pure function, which is used to create a new state on data change. Store - The store is the model or entity that holds the data. Selector - Selector to fetch the slices of data from the store to angular components. Effects - Effects deals with external network calls like API. The effect gets executed based the action performed Ngrx State Management flow: The angular component needs data for binding.  So angular component calls an action that is responsible for invoking the API call.  Aft
7 comments
Read more

Usage Of CancellationToken In Asp.Net Core Applications

When To Use CancellationToken?: In a web application request abortion or orphan, requests are quite common. On users disconnected by network interruption or navigating between multiple pages before proper response or closing of the browser, tabs make the request aborted or orphan. An orphan request can't deliver a response to the client, but it will execute all steps(like database calls, HTTP calls, etc) at the server. Complete execution of an orphan request at the server might not be a problem generally if at all requests need to work on time taking a job at the server in those cases might be nice to terminate the execution immediately. So CancellationToken can be used to terminate a request execution at the server immediately once the request is aborted or orphan. Here we are going to see some sample code snippets about implementing a CancellationToken for Entity FrameworkCore, Dapper ORM, and HttpClient calls in Asp.NetCore MVC application. Note: The sample codes I will show in
2 comments
Read more

Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication. Main Building Blocks Of Blazor WebAssembly Authentication: The core concepts of blazor webassembly authentication are: AuthenticationStateProvider Service AuthorizeView Component Task<AuthenticationState> Cascading Property CascadingAuthenticationState Component AuthorizeRouteView Component AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider. AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider
6 comments
Read more

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr
Post a Comment
Read more

Angular 14 Crud Example

In this article, we will implement CRUD operation in the Angular 14 application. Angular: Angular is a framework that can be used to build a single-page application. Angular applications are built with components that make our code simple and clean. Angular components compose of 3 files like TypeScript File(*.ts), Html File(*.html), CSS File(*.cs) Components typescript file and HTML file support 2-way binding which means data flow is bi-directional Component typescript file listens for all HTML events from the HTML file. Create Angular(14) Application: Let's create an Angular(14) application to begin our sample. Make sure to install the Angular CLI tool into our local machine because it provides easy CLI commands to play with the angular application. Command To Install Angular CLI npm install -g @angular/cli Run the below command to create the angular application. Command To Create Angular Application ng new name_of_your_app Note: While creating the app, you will see a noti
4 comments
Read more