Angular
Condivisione dei dati tra i componenti

introduzione

Osservazioni

Invio di dati dal componente principale al figlio tramite il servizio condiviso

service.ts:

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

@Injectable()
export class AppState {
  
  public mylist = [];
  
}

parent.component.ts:

import {Component} from '@angular/core';
import { AppState } from './shared.service';

@Component({
  selector: 'parent-example',
  templateUrl: 'parent.component.html',
})
export class ParentComponent {
  mylistFromParent = [];
  
  constructor(private appState: AppState){
    this.appState.mylist;
  }
  
  add() {
    this.appState.mylist.push({"itemName":"Something"});  
  }
  
}

parent.component.html:

<p> Parent </p>
  <button (click)="add()">Add</button>
<div>
  <child-component></child-component>
</div>

child.component.ts:

import {Component, Input } from '@angular/core';
import { AppState } from './shared.service';

@Component({
  selector: 'child-component',
  template: `
    <h3>Child powered by shared service</h3>
        {{mylist | json}}
  `,
})
export class ChildComponent {
  mylist: any;
  
  constructor(private appState: AppState){
    this.mylist = this.appState.mylist;
  }

}

Invia dati dal componente principale al componente figlio tramite associazione dati utilizzando @Input

parent.component.ts:

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

@Component({
  selector: 'parent-example',
  templateUrl: 'parent.component.html',
})

export class ParentComponent {
  mylistFromParent = [];
  
  add() {
    this.mylistFromParent.push({"itemName":"Something"}); 
  }
  
}

parent.component.html:

<p> Parent </p>
  <button (click)="add()">Add</button>

<div>
  <child-component [mylistFromParent]="mylistFromParent"></child-component>
</div>

child.component.ts:

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

@Component({
  selector: 'child-component',
  template: `
    <h3>Child powered by parent</h3>
        {{mylistFromParent | json}}
  `,
})

export class ChildComponent {
  @Input() mylistFromParent = [];
}

Invio di dati da bambino a genitore tramite l'emettitore di eventi @Output

eventi-emitter.component.ts

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

@Component({
  selector: 'event-emitting-child-component',
  template: `<div *ngFor="let item of data">
               <div (click)="select(item)">
                 {{item.id}} = {{ item.name}}
               </div>
             </div>
            `
})

export class EventEmitterChildComponent implements OnInit{
  
  data;
  
  @Output()
  selected: EventEmitter<string> = new EventEmitter<string>();
  
  ngOnInit(){
    this.data = [ { "id": 1, "name": "Guy Fawkes", "rate": 25 }, 
                  { "id": 2, "name": "Jeremy Corbyn", "rate": 20 }, 
                  { "id": 3, "name": "Jamie James", "rate": 12 }, 
                  { "id": 4, "name": "Phillip Wilson", "rate": 13 }, 
                  { "id": 5, "name": "Andrew Wilson", "rate": 30 }, 
                  { "id": 6, "name": "Adrian Bowles", "rate": 21 }, 
                  { "id": 7, "name": "Martha Paul", "rate": 19 }, 
                  { "id": 8, "name": "Lydia James", "rate": 14 }, 
                  { "id": 9, "name": "Amy Pond", "rate": 22 }, 
                  { "id": 10, "name": "Anthony Wade", "rate": 22 } ]
  }
  
  select(item) { 
      this.selected.emit(item);
        
  }

}

eventi-receiver.component.ts:

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

@Component({
    selector: 'event-receiver-parent-component',
    template: `<event-emitting-child-component (selected)="itemSelected($event)">
                </event-emitting-child-component>
                <p *ngIf="val">Value selected</p>
                <p style="background: skyblue">{{ val | json}}</p>`
})

export class EventReceiverParentComponent{ 
  val;
  
  itemSelected(e){
    this.val = e;
  }
}

Invio di dati asincroni da padre a figlio utilizzando Observable e Subject

shared.service.ts:

import { Injectable }    from '@angular/core';
import { Headers, Http } from '@angular/http';

import 'rxjs/add/operator/toPromise';

import { Observable } from 'rxjs/Observable';
import { Observable } from 'rxjs/Rx';
import {Subject} from 'rxjs/Subject';


@Injectable()
export class AppState {
  
  private headers = new Headers({'Content-Type': 'application/json'});
  private apiUrl = 'api/data';
  
  // Observable string source
  private dataStringSource = new Subject<string>();

  // Observable string stream
  dataString$ = this.dataStringSource.asObservable();
  
  constructor(private http: Http) { }
  
  public setData(value) {
    this.dataStringSource.next(value);
  }
  
  fetchFilterFields() {
    console.log(this.apiUrl);
    return this.http.get(this.apiUrl)
               .delay(2000)
               .toPromise()
               .then(response => response.json().data)
               .catch(this.handleError);
  }
  
  private handleError(error: any): Promise<any> {
    console.error('An error occurred', error); // for demo purposes only
    return Promise.reject(error.message || error);
  }

}

parent.component.ts:

import {Component, OnInit} from '@angular/core';
import 'rxjs/add/operator/toPromise';
import { AppState } from './shared.service';

@Component({
  selector: 'parent-component',
  template: `
              <h2> Parent </h2>
              <h4>{{promiseMarker}}</h4>

              <div>
                <child-component></child-component>
              </div>
            `
})
export class ParentComponent implements OnInit {
  
  promiseMarker = "";
  
  constructor(private appState: AppState){ }
  
  ngOnInit(){
    this.getData();
  }
  
  getData(): void {
    this.appState
        .fetchFilterFields()
        .then(data => {
          // console.log(data)
          this.appState.setData(data);
          this.promiseMarker = "Promise has sent Data!";
        });
  }
  
}

child.component.ts:

import {Component, Input } from '@angular/core';
import { AppState } from './shared.service';


@Component({
  selector: 'child-component',
  template: `
    <h3>Child powered by shared service</h3>
        {{fields | json}}
  `,
})
export class ChildComponent {
  fields: any;
  
  constructor(private appState: AppState){
    // this.mylist = this.appState.get('mylist');
  
    this.appState.dataString$.subscribe(
      data => {
        // console.log("Subs to child" + data);
        this.fields = data; 
      });
    
  }

}