A guide to integrating a component into another component in Angular

Question

A guide to integrating a component into another component in Angular

Currently, I am encountering an issue with importing a component into another in my Ionic 5.0.0 application.

Within my application, I have two separate modules: ChatPageModule and HomePageModule. My objective is to include the Chat template within the Home template (similar to ng-include) so that the home screen displays both templates simultaneously on the left and right sides.

To achieve this, I created a new module named SharedPageModule:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule } from '@angular/forms';
import { Routes, RouterModule } from '@angular/router';

import { IonicModule } from '@ionic/angular';

import { ChatPage } from '../chat/chat.page';

const routes: Routes = [
];

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    IonicModule,
    RouterModule.forChild(routes)
  ],
  declarations: [ChatPage],
  exports: [ChatPage]
})

export class SharedPageModule {}

Following that, I integrated the SharePageModule into the HomePageModule as shown below:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { IonicModule } from '@ionic/angular';
import { FormsModule } from '@angular/forms';
import { RouterModule } from '@angular/router';

import { HomePage } from './home.page';
import { SharedPageModule } from '../shared/shared.module'


@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    IonicModule,
    RouterModule.forChild([
      {
        path: '',
        component: HomePage
      }
    ]),
    SharedPageModule
  ],
  declarations: [HomePage]
})
export class HomePageModule {}

I proceeded by adding the template selector of the Chat component to the home template like so:

<ion-header>
    <ion-toolbar>
        <ion-title text-center>HOME</ion-title>                
    </ion-toolbar>
</ion-header>

<ion-content  class="homepage-content no-scroll" >
<ion-row>
...
</ion-row>

<ion-row>
 ...
 </ion-row>

<ion-row>  
<app-chat></app-chat> <!-- Included here -->
</ion-row>

</ion-content>

Everything went well up to this point, but then I encountered an issue.

I intended to call some methods from the ChatPage component within the HomePage component. To achieve this, I imported the Chat component in Home in the following manner:

import { Platform } from '@ionic/angular';
import { ChatPage } from '../chat/chat.page'

@Component({
  selector: 'app-home',
  templateUrl: 'home.page.html',
  styleUrls: ['home.page.scss'],
})
export class HomePage implements OnInit {
  
constructor(private chat: ChatPage) {}

  ngOnInit(): void {
   this.chat.getMessages();
  }
  
 }

However, upon navigating to my home page, I encountered the error detailed below:

core.js:15724 ERROR Error: Uncaught (in promise): Error: StaticInjectorError(AppModule)[HomePage -> ChatPage]: 
  StaticInjectorError(Platform: core)[HomePage -> ChatPage]: 
    NullInjectorError: No provider for ChatPage!
Error: StaticInjectorError(AppModule)[HomePage -> ChatPage]: 
  StaticInjectorError(Platform: core)[HomePage -> ChatPage]: 
    NullInjectorError: No provider for ChatPage!
    at NullInjector.push../node_modules/@angular/core/fesm5/core.js.NullInjector.get (core.js:8896)
    at resolveToken (core.js:9141)
    at tryResolveToken (core.js:9085)
    at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:8982)
    at resolveToken (core.js:9141)
    at tryResolveToken (core.js:9085)
    at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:8982)
    at resolveNgModuleDep (core.js:21218)
    at NgModuleRef_.push../node_modules/@angular/core/fesm5/core.js.NgModuleRef_.get (core.js:21907)
    at resolveNgModuleDep (core.js:21218)
    at resolvePromise (zone.js:831)
    at resolvePromise (zone.js:788)
    at zone.js:892
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:423)
    at Object.onInvokeTask (core.js:17290)
    at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:422)
    at Zone.push../node_modules/zone.js/dist/zone.js.Zone.runTask (zone.js:195)
    at drainMicroTaskQueue (zone.js:601)

angular typescript ionic4

Answer 1

Answer №1

One crucial mistake you made is failing to include a provider in your code. This can lead to errors, as shown below:

// app.page.ts

@Component({
  providers:  [LoginPage],
  selector: 'app-login',
  templateUrl: 'login.page.html',
  styleUrls: ['login.page.scss']
})

Answer 2

One crucial mistake you made is failing to include a provider in your code. This can lead to errors, as shown below:

// app.page.ts

@Component({
  providers:  [LoginPage],
  selector: 'app-login',
  templateUrl: 'login.page.html',
  styleUrls: ['login.page.scss']
})

Answer 3

Answer №2

You've mistakenly injected the ChatPage into the HomePage component. No need for injection, simply reference the ChatPage instance instead.

To achieve this, include a template variable in your HTML code and use @ViewChild to access the component and execute any desired methods.

Answer 4

You've mistakenly injected the ChatPage into the HomePage component. No need for injection, simply reference the ChatPage instance instead.

To achieve this, include a template variable in your HTML code and use @ViewChild to access the component and execute any desired methods.

Answer 5

Answer №3

The Angular standards recommend using Events to achieve this functionality:

Declare an EventEmitter in your child component with the @Output decorator to allow data to be emitted from the component:

// example.component.ts
// ...
@Output()
onExample = new EventEmitter<string>();

/* Triggered when a certain event occurs */
onAction(data: string) { onExample.emit(data) }

// ...

In your parent component template, listen for this event ($event represents the data of the event)

<app-example (onExample)="parentMethod($event)"></app-example>

If you specifically need to access the data only when the component is initialized, it is advised to use services instead of components :

// example.service.ts
// ...
private data: any[] = [];

getData(): any[] { return this.data; }

addData(item: any): void { this.data.push(item); }
// ...

You can then utilize this service in both components (Example and Home) :

// home.component.ts
// ...
constructor(private exampleService: ExampleService) {}

ngOnInit() {
  this.exampleService.getData();
}
// ...

If there is a need to call a method from the child component, @ViewChild can still be used.

Helpful Links:

Answer 6

The Angular standards recommend using Events to achieve this functionality:

Declare an EventEmitter in your child component with the @Output decorator to allow data to be emitted from the component:

// example.component.ts
// ...
@Output()
onExample = new EventEmitter<string>();

/* Triggered when a certain event occurs */
onAction(data: string) { onExample.emit(data) }

// ...

In your parent component template, listen for this event ($event represents the data of the event)

<app-example (onExample)="parentMethod($event)"></app-example>

If you specifically need to access the data only when the component is initialized, it is advised to use services instead of components :

// example.service.ts
// ...
private data: any[] = [];

getData(): any[] { return this.data; }

addData(item: any): void { this.data.push(item); }
// ...

You can then utilize this service in both components (Example and Home) :

// home.component.ts
// ...
constructor(private exampleService: ExampleService) {}

ngOnInit() {
  this.exampleService.getData();
}
// ...

If there is a need to call a method from the child component, @ViewChild can still be used.

Helpful Links:

A guide to integrating a component into another component in Angular

Answer №1

Answer №2

Answer №3

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