Angular - Dynamically inject a component in another component

Question

I'm developping a little UI components framework for my personal needs and for fun. I'm developping a Tab component and for testing purpose, I need to inject dynamically a component (TabContainerComponent) inside another component (TabComponent). Below, the code of my two components:

tab.component.ts:

import {Component, ContentChildren} from "@angular/core";
import {TabContainerComponent} from "./tabContainer.component";

@Component({
    selector: 'tab',
    templateUrl: 'tab.component.html'
})
export class TabComponent {

    @ContentChildren(TabContainerComponent)
    tabs: TabContainerComponent[];
}

tab.component.html:

<ul>
    <li *ngFor="let tab of tabs">{{ tab.title }}</li>
</ul>
<div>
    <div *ngFor="let tab of tabs">
        <ng-container *ngTemplateOutlet="tab.template"></ng-container>
    </div>
    <ng-content></ng-content>
</div>

tabContainer.component.ts:

import {Component, Input} from "@angular/core";

@Component({
    selector: 'tab-container',
    template: '<ng-container></ng-container>'
})
export class TabContainerComponent {

    @Input()
    title: string;

    @Input()
    template;
}

I used a ComponentFactoryResolver and a ComponentFactory to create dynamically my new component (TabContainerComponent), and inject it in a placeholder inside my other component (TabContainer), in the addTab method:

app.component.ts:

import {
    Component, ViewChild, ComponentFactoryResolver, ComponentFactory,
    ComponentRef, TemplateRef, ViewContainerRef
} from '@angular/core';
import {TabContainerComponent} from "./tabContainer.component";
import {TabComponent} from "./tab.component";

@Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.css']
})
export class AppComponent {

    title = 'app';

    @ViewChild(TabComponent)
    tab: TabComponent;

    @ViewChild('tabsPlaceholder', {read: ViewContainerRef})
    public tabsPlaceholder: ViewContainerRef;

    @ViewChild('newTab')
    newTab: TemplateRef<any>;

    constructor(private resolver: ComponentFactoryResolver) {
    }

    addTab(): void {
        let factory: ComponentFactory<TabContainerComponent> = this.resolver.resolveComponentFactory(TabContainerComponent);
        let tab: ComponentRef<TabContainerComponent> = this.tabsPlaceholder.createComponent(factory);
        tab.instance.title = "New tab";
        tab.instance.template = this.newTab;
        console.log('addTab() triggered');
    }
}

The addMethod is triggered by clicking on the "Add tab" button:

app.component.html:

<button (click)="addTab()">Add tab</button>
<tab>
    <tab-container title="Tab 1" [template]="tab1"></tab-container>
    <tab-container title="Tab 2" [template]="tab2"></tab-container>
    <ng-container #tabsPlaceholder></ng-container>
</tab>
<ng-template #tab1>T1 template</ng-template>
<ng-template #tab2>T2 template</ng-template>
<ng-template #newTab>
    This is a new tab
</ng-template>

app.module.ts:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';


import { AppComponent } from './app.component';
import {TabContainerComponent} from "./tabContainer.component";
import {TabComponent} from "./tab.component";


@NgModule({
    declarations: [
        AppComponent,
        TabComponent,
        TabContainerComponent
    ],
    imports: [
        BrowserModule
    ],
    providers: [],
    bootstrap: [AppComponent],
    entryComponents: [
        TabContainerComponent
    ]
})
export class AppModule { }

When I click on the "Add tab" button, I'm able to see the console.log message and I'm able to see a new <tab-container> tag (but without any attribute, which is strange) inside the <tab> tag but Angular doesn't update the Tab component view (there is no <li> and <div> created). I tried also to check changes by implementing OnChanges interface in TabComponent class but without success.

Is anyone have an idea to solve my problem ?

P.S.: I don't want to use an array of TabContainer components in order to test the createComponent method.

Update:

Demo:

https://stackblitz.com/edit/angular-imeh71?embed=1&file=src/app/app.component.ts

Given that you will inject the same component every time, why not work around this issue with a ngFor ? — user4676340
I inject the same component only for testing purpose. The injected component could be created by any logic in the app-component — Justin C.

byj byj · Accepted Answer · 2018-07-29T16:29:20

Here is the way I could make it work -

Tab.component.ts

Changed "tabs" from TabContainerComponent array to QueryList.

import { Component, ContentChildren, QueryList } from '@angular/core';
import { TabContainerComponent } from '../tab-container/tab-container.component';

@Component({
  selector: 'app-tab',
  templateUrl: 'tab.component.html'
})
export class TabComponent {
  @ContentChildren(TabContainerComponent)
  tabs: QueryList<TabContainerComponent>;

  constructor() {}
}

Added a new template in app.component.html

<ng-template #tabContainerTemplate>
  <app-tab-container title="New Tab" [template]="newTab"></app-tab-container>
</ng-template>

app.component.ts

import {
  Component,
  ViewChild,
  TemplateRef,
  ViewContainerRef,
  AfterViewInit,
  ViewChildren,
  QueryList,
  ChangeDetectorRef
} from '@angular/core';
import { TabContainerComponent } from './tab-container/tab-container.component';
import { TabComponent } from './tab/tab.component';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements AfterViewInit {
  title = 'app';
  changeId: string;
  @ViewChild(TabComponent) tab: TabComponent;
  @ViewChild('tabsPlaceholder', { read: ViewContainerRef })
  public tabsPlaceholder: ViewContainerRef;
  @ViewChild('tabContainerTemplate', { read: TemplateRef })
  tabContainerTemplate: TemplateRef<null>;
  @ViewChildren(TabContainerComponent)
  tabList: QueryList<TabContainerComponent>;

  constructor(private changeDetector: ChangeDetectorRef) {}

  ngAfterViewInit() {}

  addTab(): void {
    this.tabsPlaceholder.createEmbeddedView(this.tabContainerTemplate);
    this.tab.tabs = this.tabList;
    this.changeDetector.detectChanges();
    console.log('addTab() triggered');
  }
}

Added a ViewChildren query for TabContainerComponent. In addTab() used createEmbeddedView to add new tab container component.

I thought that "ContentChildren" query in TabComponent should be updated by the newly added component but it doesn't. I have tried to subscribe to "changes" for the query list in TabCompoent but it doesn't get triggered.

But I observed that "ViewChildren" query in AppComponent got updated every time a new component is added. So I have assigned updated QueryList of app component to the QueryList of TabComponent.

The working demo is available here

Angular - Dynamically inject a component in another component

2 Answers