Angular 2 Passing data from parent to child

Question

I pass products from the parent component to the child component using input binding, and it works the first time the child component is called. I expect changes in filterProduct () products to be reflected in the child with every change in the parent, but this does not happen. How to do it?

Parent template:

<div class="container-fluid">
<div class="col-sm-9">
    <app-product-card [products]=products></app-product-card>
</div>

Parent component:

@Component({
  selector: 'app-appliances-product-card',
  moduleId: module.id,
  templateUrl: 'appliances-product-card.component.html'
})

export class AppliancesProductCardComponent implements OnInit{    
   products: Product[];

   filterProduct(filter) {
     this.products = this.filteredProducts;         
  }
}

Children's component:

@Component({
  selector: 'app-product-card',
  moduleId: module.id,
  templateUrl: 'product-card.component.html'
})

export class ProductCardComponent {
  @Input() products: Product[];
}

Answer 1

Here's a plunker of what might work for you:

https://plnkr.co/edit/S47fBh2xdT1gp2zrznk4?p=preview

Instead of transferring data from the parent to the child component, both the parent and child component will use the service to receive data.

Parent component:

import { Component, OnInit } from '@angular/core';
import { Product } from './product'    
import { ProductsService } from './products.service';

@Component({
  selector: 'app-appliances-product-card',
  template: `
    <div class="container-fluid">
      <button (click)="filterProduct('Type 1')">Filter Type 1</button>
      <button (click)="filterProduct('')">Clear Filter</button>
      <div class="col-sm-9">
        <app-products-card></app-products-card>
      </div>
    </div>
  `
})
export class AppliancesProductCardComponent implements OnInit {
  products: Product[];      
  constructor(private _productsService: ProductsService){ }      

  filterProduct(type: string) {
    this.products = this._productsService.filterProduct(type);
  }      

  ngOnInit() { 
    this.products = this._productsService.getAllProducts();
  }
}

Children's component:

import { Component, OnInit, Input } from '@angular/core';    
import { Product } from './product';    
import { ProductsService } from './products.service';

@Component({
  selector: 'app-products-card',
  template: `
    <h1>Product Card</h1>
      <div *ngFor="let product of products">{{product.name}} - {{product.type}}</div>
  `
})
export class ProductsCardComponent implements OnInit {      
  constructor(private _productsService: ProductsService){ }

  ngOnInit() { 
    this.products = this._productsService.getAllProducts();        
    this._productsService.filteredProducts.subscribe(products => {
      console.log(products);
      this.products = products
    });
  }
}

Services:

import { EventEmitter, Injectable } from '@angular/core';    
import { Product } from './product';

export class ProductsService {
  filteredProducts = new EventEmitter<Product[]>;

  private products: Product[] = [
      { id: 1, name: 'Product 1', price: 10.50, type: 'Type 1' },
      { id: 2, name: 'Product 2', price: 15.50, type: 'Type 1' },
      { id: 3, name: 'Product 3', price: 1.50, type: 'Type 2' },
      { id: 4, name: 'Product 4', price: 100.50, type: 'Type 3' }
    ];

  getAllProducts(): Product[] {
    return this.products.slice();
  }

  filterProduct(type: string): Product[]{
    let filteredProducts = this.products.filter(p => !type || p.type == type).slice();
    this.filteredProducts.emit(filteredProducts);
  }
}

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Answer 2

, , ngOnChanges() SimpleChange @angular/core. Angular - linkComponent Interaction , :

import { Component, Input, OnChanges, SimpleChange } from '@angular/core';

@Component({
  selector: 'version-child',
  template: `
    <h3>Version {{major}}.{{minor}}</h3>
    <h4>Change log:</h4>
    <ul>
      <li *ngFor="let change of changeLog">{{change}}</li>
    </ul>
  `
})
export class VersionChildComponent implements OnChanges {
  @Input() major: number;
  @Input() minor: number;
  changeLog: string[] = [];

  ngOnChanges(changes: {[propKey: string]: SimpleChange}) {
    let log: string[] = [];
    for (let propName in changes) {
      let changedProp = changes[propName];
      let to = JSON.stringify(changedProp.currentValue);
      if (changedProp.isFirstChange()) {
        log.push(`Initial value of ${propName} set to ${to}`);
      } else {
        let from = JSON.stringify(changedProp.previousValue);
        log.push(`${propName} changed from ${from} to ${to}`);
      }
    }
    this.changeLog.push(log.join(', '));
  }
}

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

@Component({
  selector: 'version-parent',
  template: `
    <h2>Source code version</h2>
    <button (click)="newMinor()">New minor version</button>
    <button (click)="newMajor()">New major version</button>
    <version-child [major]="major" [minor]="minor"></version-child>
  `
})
export class VersionParentComponent {
  major = 1;
  minor = 23;

  newMinor() {
    this.minor++;
  }

  newMajor() {
    this.major++;
    this.minor = 0;
  }
}

Answer 3

You can use the general service for this. It can contain both data and observed to subscribe to notifications when the data is updated.

Service

export class ListService {
  list1Event: EventEmitter<any> = new EventEmitter();

  getLists() {
    return this.http.get(url).map(res => res.json())
      .subscribe(
        (data) => {
          this.list1Event.emit(data.list1);
        }
      );
  }
}

component

@Component({
  selector: 'my-component1',
  template: `
    <ul>
     <li *ngFor="#item of list">{{item.name}}</li>
    </ul>
  `
})
export class MyComponent1 {
  constructor(private service:ListService) {
    this.service.list1Event.subscribe(data => {
      this.list = data;
    });
  }
}

Answer 4

RESOLUTION USED: A variable is declared using the @ViewChild decorator in the parent component, which indicates the property in the child component.

@Component ({selector: "app-devices-product-card", moduleId: module.id, templateUrl: 'devices-product-card.component.html'})

export class AppliancesProductCardComponent implements OnInit{    
   products: Product[];

@ViewChild(ProductCardComponent )
private productCardComponent : ProductCardComponent;

   filterProduct(filter) {
     this.products = productCardComponent.product;
  }
}