Is it possible to display Angular component using Angular Interpolation?

In Angular, interpolation ({{ }}) is used for binding component class properties to text nodes in the component's template. This means you can't directly use interpolation to insert or render HTML elements or Angular components. Interpolation treats any value as a string, so if you attempt to return HTML or a component selector as a string, Angular will escape it to prevent security issues like XSS (Cross-Site Scripting) and it will be rendered as plain text in the DOM.

Given the constraints you've described, where you cannot alter the ParentComponent implementation but wish to return custom HTML or an Angular component from the ChildComponent, you are facing a limitation because Angular does not support rendering components or HTML directly through interpolation in this manner.

However, there are alternative approaches to dynamically render components or HTML within Angular applications, though they may not be applicable within your specific constraint of not being able to change the ParentComponent. These include:

Using Angular's DomSanitizer for Safe HTML Binding: If you only need to insert HTML (not an Angular component), you could use Angular's [innerHTML] binding to insert HTML content safely. You would need to sanitize the HTML content using Angular's DomSanitizer to bypass security checks. This does not directly apply to your scenario since ParentComponent's template cannot be changed.

Dynamic Component Loading: Angular provides mechanisms to dynamically load components at runtime using ViewContainerRef and ComponentFactoryResolver. This approach allows for more complex component insertion scenarios but requires a placeholder directive or a known insertion point in the parent component's template, which again, seems not to be an option in your case.

Given your constraints, the most straightforward approach you're seeking (to directly return a component from a method and have it rendered via interpolation) isn't supported by Angular's design.

A potential workaround, although not ideal and depending on your full application context, could be to re-evaluate the architecture of your solution. Consider whether:

The logic within getData() can be moved to a service if it's about data fetching or processing, allowing different components to react to this data in their unique ways. The child component can use ng-content or template outlets to project content into the parent, although this would require changes to how the parent component is structured. In scenarios where you're locked into a specific architecture without the ability to change the parent component, the best course of action might be to rethink the interaction patterns between your components or resort to using native JavaScript solutions outside of the Angular context, which comes with its own set of challenges and is generally not recommended.

Directive for Dynamic HTML Content Here's how you might set up a directive to dynamically insert HTML. This assumes you have some way to apply this directive in the desired location within your templates.

// dynamic-html.directive.ts
import { Directive, Input, ElementRef, OnInit, Renderer2, SecurityContext } from '@angular/core';
import { DomSanitizer } from '@angular/platform-browser';

@Directive({
  selector: '[appDynamicHtml]'
})
export class DynamicHtmlDirective implements OnInit {
  @Input() appDynamicHtml: string;

  constructor(private elementRef: ElementRef, private renderer: Renderer2, private sanitizer: DomSanitizer) {}

  ngOnInit(): void {
    const sanitizedHtml = this.sanitizer.sanitize(SecurityContext.HTML, this.appDynamicHtml);
    if (sanitizedHtml) {
      this.renderer.setProperty(this.elementRef.nativeElement, 'innerHTML', sanitizedHtml);
    }
  }
}

Applying the Directive Assuming you could add a directive to the ParentComponent's template (which you mentioned is not possible), the directive would be used as follows:

<!-- In parent or child component template -->
<div appDynamicHtml="{{ getData() }}"></div>

We can simply use innerHTML to render the html content, but you need to make few corrections

• only the class is inherited not the decorator contents, so we need to define the selector and html template for the child!

• we need to add override prefix for getData since we are overriding the inherited method!

parent and child

import { Component } from '@angular/core';

@Component({
  selector: 'app-parent',
  standalone: true,
  template: `
    <div>
      Parent Component:
      <div>{{ getData() }}</div>
    </div>
  `,
})
export class ParentComponent {
  getData(): string {
    return 'My Title'; // This will be overridden by the child component
  }
}

@Component({
  selector: 'app-child',
  standalone: true,
  template: `
  <div>
    Child Component:
    <div [innerHTML]="getData()"></div>
  </div>
    `,
})
export class ChildComponent extends ParentComponent {
  override getData(): string {
    return '<h2>My Title</h2>'; // Custom HTML string
  }
}

main.ts

import { Component } from '@angular/core';
import { bootstrapApplication } from '@angular/platform-browser';
import 'zone.js';
import { ChildComponent, ParentComponent } from './test';

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [ParentComponent, ChildComponent],
  template: `
    <app-parent/>
    <hr/>
    <app-child/>
  `,
})
export class App {
  name = 'Angular';
}

bootstrapApplication(App);

stackblitz demo