How to Dynamically Create Components in Angular 6 with ViewChild?

Introduction In Angular applications, especially when dealing with dynamic components, it's common to face challenges related to identifying and managing multiple instances of components. For instance, you might want to dynamically load components within an accordion, leveraging Angular's templating features like and , ensuring that each instance can be referenced correctly using @ViewChild. In this article, we’ll explore how to achieve dynamic component loading in an Angular 6 application, addressing the specific scenario you described. Understanding the Problem You’re trying to create an accordion with dynamic components where every div for dynamic insertion needs a unique reference. When you loop through a list of items, Angular does not automatically bind the ViewChild references that you define with a template variable (#) when using the ngFor directive, which results in the ViewContainerRef being undefined. This happens because Angular creates a new context for each iteration of ngFor which doesn’t allow for direct manipulation of variable scopes, leading to the inability of @ViewChild to recognize your dynamically generated references. Suggested Solution To effectively control dynamic components within ngFor, you can use the ViewChild in combination with the @ViewChildren decorator, which allows for the retrieval of multiple references from the DOM. Here’s how you can implement it: Step 1: Modify Your Template Use ng-container to create a structure that allows for component creation dynamically within the loop: {{item.name}} Step 2: Update Your Component Class Replace your @ViewChild with @ViewChildren to collect references to all dynamic containers: import { Component, ViewChildren, QueryList, ViewContainerRef, AfterViewInit } from '@angular/core'; @Component({ selector: 'your-selector', templateUrl: './your-template.component.html', }) export class YourComponent implements AfterViewInit { @ViewChildren('dynamicContainer', { read: ViewContainerRef }) dynamicContainers: QueryList; ngAfterViewInit() { this.loadDynamicComponents(); } loadDynamicComponents() { this.dynamicContainers.forEach((container, index) => { // Load your dynamic component here // e.g., container.clear(); and container.createComponent(YourDynamicComponent); }); } toggle(index: number) { // Add logic to handle accordion toggle } add() { // Add logic to handle the addition of more components } } Explanation Using ng-container: Allows you to utilize structural directives like ngFor without adding extra elements to the DOM. @ViewChildren: This query will capture all instances specified with the #dynamicContainer reference, thus allowing you to manipulate them easily in your component logic. This ensures no loss of reference when looping through items. Step 3: Dynamic Component Loading To load your dynamic component into the specified containers, use the loadDynamicComponents method. Here, you utilize the ViewContainerRef to create instances of your components dynamically: import { YourDynamicComponent } from './your-dynamic.component'; loadDynamicComponents() { this.dynamicContainers.forEach((container, index) => { const componentRef = container.createComponent(YourDynamicComponent); // You can then set inputs or other properties on componentRef }); } Frequently Asked Questions 1. Can I use id instead of ViewChild for dynamic references? No, using IDs to reference dynamic components created within an *ngFor directive won't yield the results you need due to the way Angular manages scope and view encapsulations. 2. How do I maintain component state when updating? To retain the state of dynamically loaded components, consider using a service to manage shared state or ensuring inputs are properly set when re-creating instances. 3. Is there an Angular lifecycle hook for dynamic components? Yes, you can use ngAfterViewInit to execute code after your dynamic components are initialized, or use ngOnInit within your dynamic component for its own initialization logic. Conclusion By following this structured approach, you can effectively manage dynamic component creation within an Angular accordion. Remember to utilize @ViewChildren for capturing multiple ViewContainerRef instances, ensuring a robust and maintainable codebase. This method can be applied broadly across components where dynamic features are necessary.

May 8, 2025 - 08:52

How to Dynamically Create Components in Angular 6 with ViewChild?

Introduction

In Angular applications, especially when dealing with dynamic components, it's common to face challenges related to identifying and managing multiple instances of components. For instance, you might want to dynamically load components within an accordion, leveraging Angular's templating features like and , ensuring that each instance can be referenced correctly using @ViewChild.

In this article, we’ll explore how to achieve dynamic component loading in an Angular 6 application, addressing the specific scenario you described.

Understanding the Problem

You’re trying to create an accordion with dynamic components where every div for dynamic insertion needs a unique reference. When you loop through a list of items, Angular does not automatically bind the ViewChild references that you define with a template variable (#) when using the *ngFor directive, which results in the ViewContainerRef being undefined.

This happens because Angular creates a new context for each iteration of *ngFor which doesn’t allow for direct manipulation of variable scopes, leading to the inability of @ViewChild to recognize your dynamically generated references.

Suggested Solution

To effectively control dynamic components within *ngFor, you can use the ViewChild in combination with the @ViewChildren decorator, which allows for the retrieval of multiple references from the DOM. Here’s how you can implement it:

Step 1: Modify Your Template

Use ng-container to create a structure that allows for component creation dynamically within the loop:

Step 2: Update Your Component Class

Replace your @ViewChild with @ViewChildren to collect references to all dynamic containers:

import { Component, ViewChildren, QueryList, ViewContainerRef, AfterViewInit } from '@angular/core';

@Component({
  selector: 'your-selector',
  templateUrl: './your-template.component.html',
})
export class YourComponent implements AfterViewInit {
  @ViewChildren('dynamicContainer', { read: ViewContainerRef }) dynamicContainers: QueryList;

  ngAfterViewInit() {
    this.loadDynamicComponents();
  }

  loadDynamicComponents() {
    this.dynamicContainers.forEach((container, index) => {
      // Load your dynamic component here
      // e.g., container.clear(); and container.createComponent(YourDynamicComponent);
    });
  }

  toggle(index: number) {
    // Add logic to handle accordion toggle
  }

  add() {
    // Add logic to handle the addition of more components
  }
}

Explanation

Using ng-container: Allows you to utilize structural directives like *ngFor without adding extra elements to the DOM.
@ViewChildren: This query will capture all instances specified with the #dynamicContainer reference, thus allowing you to manipulate them easily in your component logic. This ensures no loss of reference when looping through items.

Step 3: Dynamic Component Loading

To load your dynamic component into the specified containers, use the loadDynamicComponents method. Here, you utilize the ViewContainerRef to create instances of your components dynamically:

import { YourDynamicComponent } from './your-dynamic.component';

loadDynamicComponents() {
  this.dynamicContainers.forEach((container, index) => {
    const componentRef = container.createComponent(YourDynamicComponent);
    // You can then set inputs or other properties on componentRef
  });
}

Frequently Asked Questions

1. Can I use id instead of ViewChild for dynamic references?

No, using IDs to reference dynamic components created within an *ngFor directive won't yield the results you need due to the way Angular manages scope and view encapsulations.

2. How do I maintain component state when updating?

To retain the state of dynamically loaded components, consider using a service to manage shared state or ensuring inputs are properly set when re-creating instances.

3. Is there an Angular lifecycle hook for dynamic components?

Yes, you can use ngAfterViewInit to execute code after your dynamic components are initialized, or use ngOnInit within your dynamic component for its own initialization logic.

Conclusion

By following this structured approach, you can effectively manage dynamic component creation within an Angular accordion. Remember to utilize @ViewChildren for capturing multiple ViewContainerRef instances, ensuring a robust and maintainable codebase. This method can be applied broadly across components where dynamic features are necessary.