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How do I use #ViewChild with an external ng-template (Angular 11)

THE PROBLEM
So I have two Angular components, a parent and a child. The parent passes a custom template to the child component, which then hydrates the template with its own data using ngTemplateOutlet.
This works well for the most part. Unfortunately, I run into issues when trying to access the DOM elements of this parent template from the child.
If I try to access <div #container></div> from the default child template using #ViewChild('container',{static: false}), it gets the element without issue. When I do the same using the custom template passed in by app.component, I get the error "cannot read property 'nativeElement' of undefined".
What else do I have to do to access the DOM of my template?
Here's a Stackblitz
App.Component (Parent)
import { Component } from "#angular/core";
#Component({
selector: "my-app",
templateUrl: "./app.component.html",
styleUrls: ["./app.component.css"]
})
export class AppComponent {}
<child [customTemplate]="parentTemplate"></child>
<ng-template #parentTemplate let-context="context">
<div #container>HELLO FROM CONTAINER</div>
<button (click)="context.toggleShow()">Toggle Display</button>
<div *ngIf="context.canShow">Container contains the text: {{context.getContainerText()}}</div>
</ng-template>
child.component (Child)
import {
Component,
ElementRef,
Input,
TemplateRef,
ViewChild
} from "#angular/core";
#Component({
selector: "child",
templateUrl: "./child.component.html",
styleUrls: ["./child.component.css"]
})
export class ChildComponent {
#Input() public customTemplate!: TemplateRef<HTMLElement>;
#ViewChild("container", { static: false })
public readonly containerRef!: ElementRef;
templateContext = { context: this };
canShow: boolean = false;
toggleShow() {
this.canShow = !this.canShow;
}
getContainerText() {
return this.containerRef.nativeElement.textContent;
}
}
<ng-container *ngTemplateOutlet="customTemplate || defaultTemplate; context: templateContext">
</ng-container>
<ng-template #defaultTemplate>
<div #container>GOODBYE FROM CONTAINER</div>
<button (click)="toggleShow()">Toggle Display</button>
<div *ngIf="canShow">Container contains the text: {{getContainerText()}}</div>
</ng-template>
MY QUESTION
How do I use #ViewChild to access this div from an outside template that updates with any changes in the DOM? (Note: Removing the *ngIf is NOT an option for this project)
What's causing this? Are there any lifecycle methods that I can use to remedy this issue?
MY HUNCH
I'm guessing that ViewChild is being called BEFORE the DOM updates with its new template and I need to setup a listener for DOM changes. I tried this and failed so I'd really appreciate some wisdom on how best to proceed. Thanks in advance :)
EDIT:
This solution needs to properly display <div #container></div> regardless of whether you're passing in a custom template or using the default one.

ViewChild doesn't seem to pick up a rendered template - probably because it's not part of the components template initially. It's not a timing or lifecycle issue, it's just never available as a ViewChild
An approach that does work is to pass in the template as content to the child component, and access it using ContentChildren. You subscribe to the ContentChildren QueryList for changes, which will update when the DOM element becomes rendered
You can then access the nativeElement (the div). If you wanted you could add listeners here to the DOM element, and trigger cd.detectChanges afterwards, but that would be a bit unusual. It would probably be better to handle DOM changes in the parent element, and pass the required values down to the child using regular #Input on the child
#Component({
selector: "my-app",
template: `
<child>
<ng-template #parentTemplate let-context="context">
<div #container>Parent Template</div>
</ng-template>
</child>
`,
styleUrls: ["./app.component.css"]
})
export class AppComponent {}
#Component({
selector: "child",
template: `
<ng-container *ngTemplateOutlet="customTemplate"> </ng-container>
`,
styleUrls: ["./child.component.css"]
})
export class ChildComponent implements AfterContentInit {
#ContentChild("parentTemplate")
customTemplate: TemplateRef<any>;
#ContentChildren("container")
containerList: QueryList<HTMLElement>;
ngAfterContentInit() {
this.containerList.changes.subscribe(list => {
console.log(list.first.nativeElement.innerText);
// prints 'Parent Template'
});
}
}

How to pass data from child component to parent component when button clicked on parent component

I need to pass input's value from child component to parent component when user click on a submit button that exists in parent component.
childComp template
<input
type="password"
[(ngModel)]="userPasswordForm.inputId"
class="mr-password-field k-textbox"
/>
childComp TS file
export class PasswordInputComponent{
constructor() { }
#Output() inputValue = new EventEmitter<string>();
userPasswordForm:any={'input':''};
emitValue(value: string) {
this.inputValue.emit(value);
}
}
Parent Component Template
<child-component (inputValue)="" > </child-component>
<button (click)="getValueFromChild()"> </button>
Parent Component TS file
tempUserFormPasswords:any=[];
.
.
.
getValueFromChild(receivedVal){
this.tempUserFormPasswords.push(receivedVal);
}
It would easy to dio it if the button exists inside the child component. but in this case the value should be passed when the button in the parent component is clicked!

For single ChildComponent:
Use ViewChild
For multiple ChildComponent use: ViewChildren
Parent Component TS file
Single Child Component:
tempUserFormPasswords:any=[];
#ViewChild(ChildComponent) child: ChildComponent;
.
.
.
getValueFromChild(receivedVal){
var data = child.getData();
this.tempUserFormPasswords.push(data);
}
Multiple Child Component:
tempUserFormPasswords:any=[];
#ViewChildren(ChildComponent) child: ChildComponent;
#ViewChildren(ChildComponent) children: QueryList<ChildComponent>;
.
.
.
getValueFromChild(receivedVal){
let data;
children.forEach(child => (data = this.updateData(child.data));
this.tempUserFormPasswords.push(data);
}

Create a BehaviorSubject in service file
#Injectable()
export class dataService {
data: BehaviorSubject<any> = new BehaviorSubject<any>(null);
public setData(data: any){
this.data.next(data);
}
public getData(): Observable<any> {
return this.data.asObservable();
}
}
You need to subscribe the data in your child component
PasswordInputComponent
export class PasswordInputComponent{
constructor(private service: dataService) {
this.service.getData().subscribe((data) => {
//Emit the event here
this.inputValue.emit(value);
});
}
#Output() inputValue = new EventEmitter<string>();
userPasswordForm:any={'input':''};
emitValue(value: string) {
this.inputValue.emit(value);
}
}
ParentComponent.ts
tempUserFormPasswords:any=[];
.
.
.
constructor(private service: dataService) { }
getValueFromChild(receivedVal){
this.service.setData('');
this.tempUserFormPasswords.push(receivedVal);
}
When a button clicked on the parent component we are setting the data behaviour subject, when a new value added to that it will automatically subscribed in child component.so, on that time we need to emit a event.
I think this will help you..

Read about Input and Output decorators in angular!
documentation: sharing-data.
Examples: examples

You can do it with ViewChild as already said in the other answer from #Raz Ronen. But keep in mind that depending on the Angular version, you might need to wait for the AfterViewInit lifecycle hook to be executed to interact with the child (or the child won't be available since it's not initialized).
Also, you can do it with a BehaviorSubject, like #Msk Satheesh just answered, and it's perfectly fine too. But it might be considered a bit overkill for such a simple use case.
(this is what we usually do when we don't have a relation between the components e.g one component is not children of the other one)
What I suggest is I think the simplest of all (again, their answers are not bad by any means);
It is basically the same of #Msk Satheesh (but under the hood), just a bit more Angular styled: Output + EventEmitter:
Parent component:
import { Component } from '#angular/core';
#Component({
selector: 'app-parent',
template: `
Message: {{message}}
<app-child (messageEvent)="receiveMessage($event)"></app-child>
`,
styleUrls: ['./parent.component.css']
})
export class ParentComponent {
constructor() { }
message:string;
receiveMessage($event) {
this.message = $event
}
}
Children Component:
import { Component, Output, EventEmitter } from '#angular/core';
#Component({
selector: 'app-child',
template: `
<button (click)="sendMessage()">Send Message</button>
`,
styleUrls: ['./child.component.css']
})
export class ChildComponent {
message: string = "a string from child component"
#Output() messageEvent = new EventEmitter<string>();
constructor() { }
sendMessage() {
this.messageEvent.emit(this.message)
}
}
With the code, the parent will always be subscribed to the messageEvent that’s outputted by the child component, and it will run the function (the message function) after the child emits. Handling this with Angular has the advantage that we are sure that we don't have any memory leak in our app (e.g missing unsubscriptions).
When the component that is listening (the subscribed parent) gets destroyed, Angular will unsubscribe automatically to avoid potential memory leaks.

Access text (not instance of another component) with ContentChild

How can I access a string of text given within the tags of a component
<my-custom-component>THIS TEXT</my-custom-component>
Within a template, I can use ng-content, or if it is an instance of some other class I can access it within the component definition like demonstrated in these examples. However I am interested in detecting if there is a string of text there or not, which I believe would make providedText undefined. However, I am always getting undefined.
#ContentChild(Element, { static: true }) providedText: Text | undefined;
I have tried Text as the first element passed to #ContentChild. Passing any will not work (I don't know why).
StackBlitz
I am interested mostly in finding if there is a string or undefined, but am also curious why ContentChild(Text... isn't working.
Edit:
I have added a potential solution, but it seems pretty imperfect, so I hope something better comes along.
Edit 2:
I now understand that #ContentChild is not a mechanism for selecting whatever native HTML I want without wiring it up to Angular’s dependency graph with a ref, directive, etc.
I am still curious if my proposed solution below is a bad idea for any reason.

My solution for now (since I wish to capture all transcluded content) is to wrap ng-content in a containing element, then get its innerText.
#Component({
selector: "app-parent",
template: `
<span #transcludedContainerRef>
<ng-content></ng-content>
</span>
`
})
export class ParentComponent implements AfterViewInit {
#ViewChild("transcludedContainerRef", { static: false })
transcludedContainerRef: ElementRef | undefined;
buttonText: string;
ngAfterViewInit() {
const isButtonTextPresent = this.transcludedContainerRef.nativeElement
.innerText;
if (isButtonTextPresent) {
console.log(isButtonTextPresent); // successfully logs content
}else {
console.log('No text set');
}
}
}
It does feel hacky, but it works. I am holding out for something better.

it's difficult if I don't know about your <my-custom-component>
In general if your custom component it's only
<ng-content></ng-content>
You can inject in constructor the elementRef
constructor(public el:ElementRef){}
From a parent
<hello >
Start editing to see some magic happen :)
</hello>
You can use
#ViewChild(HelloComponent,{static:false}) helloComponent:HelloComponent
click()
{
console.log(this.helloComponent.el.nativeElement.innerHTML)
}
If your component has any variable -or ViewContent-, you can access this variables in a similar way

So the other way to read the inner text from the component is that child component emit the value whatever it get's as input from other component. See below:
hello.component.ts
import { Component, Input, Output, EventEmitter, OnInit } from '#angular/core';
#Component({
selector: 'hello',
template: `<h1>Hello {{name}}!</h1>`,
styles: [`h1 { font-family: Lato; }`]
})
export class HelloComponent implements OnInit {
#Input() name: string;
#Output() innerText: EventEmitter<string> = new EventEmitter();
ngOnInit() {
this.innerText.emit(this.name);
}
}
app.component.ts
import { Component, ContentChild, AfterContentInit, OnInit } from "#angular/core";
#Component({
selector: "app-parent",
template: "content from <code>app-parent</code>"
})
export class ParentComponent implements AfterContentInit {
#ContentChild(Element, { static: true }) providedText: Text | undefined;
ngAfterContentInit() {
console.log("ngAfterContentInit Content text: ", this.providedText);
}
}
#Component({
selector: "my-app",
templateUrl: "./app.component.html",
styleUrls: ["./app.component.css"]
})
export class AppComponent {
name = "Angular";
_innerText: string;
ngAfterContentInit() {}
get childContent(): string {
return this._innerText;
}
set childContent(text) {
this._innerText = text;
}
innerTextFn(innertext: string) {
this.childContent = innertext;
console.log('Event: ', innertext);
}
}
app.component.html
<hello name="{{ name }}" (innerText)="innerTextFn($event)"></hello>
<app-parent>This is the content text</app-parent>
Here is stackblitz url to check: https://stackblitz.com/edit/angular-bacizp
I hope this may helpful for you and if yes then accept this as correct answer.

How to call other component function from different component?

I've html structure like this :
Parent Component where both Comp1 and Comp2 resides :
now in comp1 I've some elements if that changes then I've to reflect values in comp2 but there's no connection between them.
Comp1 :
import { Component } from '#angular/core';
import { Comp2Component } from 'comp2.component';
#Component({
selector: 'comp1',
templateUrl: './comp1.html'
})
export class Comp1Component {
sortBy(value)
{
this.FeedSortBy = value;
this.SortByLabel = this.SortByLabelList[value];
Comp2Component.filterActivities();
}
}
Comp2
import { Component } from '#angular/core';
#Component({
selector: 'comp2',
templateUrl: './comp2.html'
})
export class Comp2Component {
filterActivities()
{
//call this function on comp1 sort function call so it will update value of comp2
}
}
As per Rahul and Sajit's answer I try using with EventEmitter and change my structure to parent child :
In my parent component I use :
import { Component,EventEmitter, Input, Output, OnInit } from '#angular/core';
import { FeedsComponent } from '../feeds/feeds.component';
#Component({
selector: 'my-desk',
styleUrls: ['../../assets/css/style.min.css'],
templateUrl: './my-desk.component.html'
})
export class MyDeskComponent {
#Output() FeedSortBy = new EventEmitter<string>();
sortBy(value)
{
this.FeedSortBy.emit(value);
}
}
and in my child component I use :
import { Component, OnInit, Input, Output } from '#angular/core';
import { DataService } from '../data.service';
declare var $: any;
#Component({
selector: 'feeds',
styleUrls: ['../../assets/css/style.min.css'],
templateUrl: './feeds.component.html'
})
export class FeedsComponent {
constructor(private dataService:DataService)
{
}
#Input() FeedSortBy:number = 2;
}
Child component HTML :
{{FeedSortBy}}
But it always output 2 it doesn't change can I get any trigger as well to know if value is change so I call function there

You cannot do that, There are two possible ways you could achieve this,
use angular service to pass the data between two components
use Event Emitters to pass the value among the components.

You can call method of another component from a different component but it will not update the value of the calling component without some tweaking like
Event Emitters if they have a parent child relationship or Shared Services or using ngrx redux pattern
How to Call a different component method be like
Component1
test(){
console.log("Test");
}
Component 2
working(){
let component = new Component1();
component.test();
}
Now to update the value in component 2 you might have to use any of the above.
For Event Emitters follow this link
For Shared services follow this link
For ngrx follow this link

Angular #Output not working

Trying to do child to parent communication with #Output event emitter but is no working
here is the child component
import { Component, OnInit, Output, Input, EventEmitter } from '#angular/core';
#Component({
selector: 'app-emiter',
templateUrl: './emiter.component.html',
styleUrls: ['./emiter.component.css']
})
export class EmiterComponent implements OnInit {
#Output() emitor: EventEmitter<any>
constructor() { this.emitor = new EventEmitter()}
touchHere(){this.emitor.emit('Should Work');
console.log('<><><><>',this.emitor) // this comes empty
}
ngOnInit() {
}
}
this is the html template
<p>
<button (click)=" touchHere()" class="btn btn-success btn-block">touch</button>
</p>
The console.log inside the touchHere it shows nothing
even if I put this inside the parent component it show nothing as well
parent component
import { Component , OnInit} from '#angular/core';
// service I use for other stuff//
import { SenderService } from './sender.service';
// I dont know if I have to import this but did it just in case
import { EmiterComponent } from './emiter/emiter.component'
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
title = 'app';
user: any;
touchThis(message: string) {
console.log('Not working: ${message}');
}
constructor(private mySessionService: SenderService) { }
}
and here is the html template
<div>
<app-emiter>(touchHere)='touchThis($event)'</app-emiter>
</div>

Parent component template:
<app-emitor (emitor)='touchThis($event)'></app-emiter>
In parent template #Output should be 'called', not the child method.
Also, see: https://angular.io/guide/component-interaction#parent-listens-for-child-event

Here’s an example of how we write a component that has outputs:
#Component({
selector: 'single-component',
template: `<button (click)="liked()">Like it?</button>`
})
class SingleComponent {
#Output() putRingOnIt: EventEmitter<string>;
constructor() {
this.putRingOnIt = new EventEmitter();
}
liked(): void {
this.putRingOnIt.emit("oh oh oh");
}
}
Notice that we did all three steps: 1. specified outputs, 2. created an EventEmitter that we attached
to the output property putRingOnIt and 3. Emitted an event when liked is called.
If we wanted to use this output in a parent component we could do something like this:
#Component({
selector: 'club',
template: `
<div>
<single-component
(putRingOnIt)="ringWasPlaced($event)"
></single-component>
</div>`
})
class ClubComponent {
ringWasPlaced(message: string) { console.log(`Put your hands up: ${message}`);
} }
// logged -> "Put your hands up: oh oh oh"
Again, notice that:
putRingOnIt comes from the outputs of SingleComponent
ringWasPlaced is a function on the ClubComponent
$event contains the thing that wasemitted, in this case a string

<app-emiter (emitor)="touchThis($event)" ></app-emiter>
By using #Output() you should apply the event you need to emit in the directive of the emitter component.Adding the name of the variable to the the directive and but the emitted over function inside the quotation passing the $event.

touchHere() is the method from which you are binding some value to emit with your EventEmitter. And your EventEmitter is 'emitor'.
So your code will work if you simply do the below:
<app-emiter (emitor)='touchThis($event)'></app-emiter>