[angular] 부모 클래스에서 자식 구성 요소 메서드 호출-Angular

호출하려는 메서드가있는 자식 구성 요소를 만들었습니다.

이 메서드를 호출하면 console.log()줄만 실행 하고 test속성을 설정하지 않습니까 ??

아래는 변경 사항이 적용된 빠른 시작 Angular 앱입니다.

부모의

import { Component } from '@angular/core';
import { NotifyComponent }  from './notify.component';

@Component({
    selector: 'my-app',
    template:
    `
    <button (click)="submit()">Call Child Component Method</button>
    `
})
export class AppComponent {
    private notify: NotifyComponent;

    constructor() {
      this.notify = new NotifyComponent();
    }

    submit(): void {
        // execute child component method
        notify.callMethod();
    }
}

아이

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

@Component({
    selector: 'notify',
    template: '<h3>Notify {{test}}</h3>'
})
export class NotifyComponent implements OnInit {
   test:string;
   constructor() { }

    ngOnInit() { }

    callMethod(): void {
        console.log('successfully executed.');
        this.test = 'Me';
    }
}

test속성도 어떻게 설정할 수 있습니까?

답변

@Component({
  selector: 'child-cmp',
  template: '<p>child</p>'
})
class ChildCmp {
  doSomething() {}
}

@Component({
  selector: 'some-cmp',
  template: '<child-cmp></child-cmp>',
  directives: [ChildCmp]
})
class SomeCmp {

  @ViewChild(ChildCmp) child:ChildCmp;

  ngAfterViewInit() {
    // child is set
    this.child.doSomething();
  }
}

@Component({
  selector: 'child-cmp',
  template: '<p>child</p>'
})
class ChildCmp {
  doSomething() {}
}

@Component({
  selector: 'some-cmp',
  template: '<child-cmp #child></child-cmp>',
  directives: [ChildCmp]
})
class SomeCmp {

  @ViewChild('child') child:ChildCmp;

  ngAfterViewInit() {
    // child is set
    this.child.doSomething();
  }
}

    import { Component, OnInit, ViewChild } from '@angular/core';
    import { ChildComponent } from '../child/child';
    @Component({
               selector: 'parent-app',
               template: `<child-cmp></child-cmp>`
              })
    export class parentComponent implements OnInit{
        @ViewChild(ChildComponent ) child: ChildComponent ;

        ngOnInit() {
           this.child.ChildTestCmp(); }
}

import { Component } from '@angular/core';
@Component({
  selector: 'child-cmp',
  template: `<h2> Show Child Component</h2><br/><p> {{test }}</p> `
})
export class ChildComponent {
  test: string;
  ChildTestCmp()
  {
    this.test = "I am child component!";
  }
 }

import {Subject} from 'rxjs/Subject';
...
export class ParentComp {
    changingValue: Subject<boolean> = new Subject();
    tellChild(){
    this.changingValue.next(true);
  }
}

<my-comp [changing]="changingValue"></my-comp>

...
export class ChildComp implements OnInit{
@Input() changing: Subject<boolean>;
ngOnInit(){
  this.changing.subscribe(v => {
     console.log('value is changing', v);
  });
}

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

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

<p>
  This is child
</p>

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

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

  doSomething() {
    console.log('do something');
  }
}

export class Notifier {
    valueChanged: (data: number) => void = (d: number) => { };
}

export class Parent {
    notifyObj = new Notifier();
    tellChild(newValue: number) {
        this.notifyObj.valueChanged(newValue); // inform child
    }
}

<my-child-comp [notify]="notifyObj"></my-child-comp>

export class ChildComp implements OnInit{
    @Input() notify = new Notifier(); // create object to satisfy typescript
    ngOnInit(){
      this.notify.valueChanged = (d: number) => {
            console.log(`Parent has notified changes to ${d}`);
            // do something with the new value 
        };
    }
 }

    import import { AfterViewInit, ViewChild } from '@angular/core';
    import { Component } from '@angular/core';
    import { CountdownTimerComponent }  from './countdown-timer.component';
    @Component({
        selector: 'app-countdown-parent-vc',
        templateUrl: 'app-countdown-parent-vc.html',
        styleUrl: [app-countdown-parent-vc.css]
    export class CreateCategoryComponent implements OnInit {
         @ViewChild(CountdownTimerComponent, {static: false})
         private timerComponent: CountdownTimerComponent;
         ngAfterViewInit() {
             this.timerComponent.startTimer();
         }

         submitNewCategory(){
            this.ngAfterViewInit();
         }

<form (ngSubmit)='selX' [formGroup]="xSelForm">
    <select formControlName="xSelector">
      ...
    </select>
<button type="submit">Submit</button>
</form>
<child [selectedX]="selectedX"></child>

selX(){
  this.selectedX = this.xSelForm.value['xSelector'];
}

export class ChildComponent implements OnChanges {
  @Input() public selectedX;

  //ngOnChanges will execute if there is a change in the value of selectedX which has been passed to child as an @Input.

  ngOnChanges(changes: { [propKey: string]: SimpleChange }) {
    this.childFunction();
  }
  childFunction(){ }
}