Angular：如何访问父组件中的子组件模板变量？

Question

I am trying to access #temp of modalconfirm.component.html in parent app.component.ts but its always null.

modalconfirm.component.html

<button type="button" class="btn btn-primary" (click)="openModal(template)">Open modal</button>
<br><br>
<pre class="card card-block card-header">{{message}}</pre>
<ng-template #template>
  <div class="modal-body text-center">
    <p>Do you want to confirm?</p>
    <button type="button" class="btn btn-default" (click)="confirm()" >Yes</button>
    <button type="button" class="btn btn-primary" (click)="decline()" >No</button>
  </div>
</ng-template>

app.component.ts

import { Component, TemplateRef, ViewChild, ElementRef } from '@angular/core';
import { BsModalRef } from 'ngx-bootstrap/modal';

import { BsModalService } from 'ngx-bootstrap/modal';
import { ModalcomfirmComponent } from './modalcomfirm/modalcomfirm.component';


@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',

   template:`
  <modalcomfirm ></modalcomfirm>

  <table>
  <tr><td><div (click)="TestChild()">1</div></td></tr>
  <tr><td><div>2</div></td></tr>
  ` 
 // styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'app';

  @ViewChild("template") inputChild: ElementRef;

  @ViewChild(ModalcomfirmComponent ) child: ModalcomfirmComponent; 
TestChild(){
  console.log(this.inputChild); //undefined

}
ngOnInit(){

}
  confirmParent(evt) {
    console.log(evt);
 }

}

Answer 1

You can't access template variable of child components directly.

Template variables can only be referenced in the same tamplate you define them .

But if you are trying to get the result (confirm/decline) value from the modal child component, you can do it through @Output decorator and EventEmitter s.

See Angular - Component Interaction and Angular - Template Syntax > Input and Output properties

Also, take a look here to read about smart (containers) and dumb (presentational) components.

Answer 2

Hello try by using you the @Input and @Output decorators on properties to communicate between the two components.

The Output decorator works like callback to return a value from child component, and the Input is used to send a parameter to a child component.

Example:

    import { Component, Input, EventEmitter, Output } from '@angular/core';

    @Component({
        selector: 'child-element',
        templateUrl: './child.component.html',
        styleUrls: ['./child.component.css']
    })
    export class ChildComponent implements OnChanges {
        @Input() value: number;
        counter: number;
        @Output() valueOutput: EventEmitter<string> =
                new EventEmitter<string>();

        ngOnChanges(): void {
            this.counter++;
            this.value= this.counter;

            this.valueOutput.emit(`The value${this.value} isChanged!`); 

        }

    }

//this.valueOutput.emit must be used when you want to return a value to the parent component

//implementation in parent  html templeate
<child-element [value]='valueInParent' (valueOutput)='functionInParent()' ></child-element>

valueInParent is going to be a parameter or value that you want to send to child component, and functionInParent is going to be a function in your parent component, it resieve as a callback the child response.

Answer Reference