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How do I push data from a Subject observable to an array in the component?

I am trying to push a message into an array that is already declared as a variable in the component. I am using a service and have created a subject observable to take data from one component and inject it into another component. When I try to push the data onto the array after subscribing to the variable, it's updated temporarily but when I open that component, the data is not pushed. The array updates when I console log from inside the subscribe method but it's reset once I open that component. I don't know what is the problem. This is the code:
Service.ts
import { Injectable } from '#angular/core';
import { User } from './user';
import { Subject } from 'rxjs';
#Injectable({
providedIn: 'root'
})
export class SerService {
private message = new Subject<string>();
sourceMessage$ = this.message.asObservable();
constructor() { }
sendMessage(message: string) {
this.message.next(message);
}
}
Receiver component
import { Component, OnInit } from '#angular/core';
import { SerService } from '../ser.service';
import { User } from "../user";
#Component({
selector: 'app-login',
templateUrl: './login.component.html',
styleUrls: ['./login.component.css']
})
export class LoginComponent implements OnInit {
public messages = ['hi', 'hello', 'bye'];
constructor(private _service: Service) { }
ngOnInit() {
this._service.message$
.subscribe(
message => {
this.messages.push(message);
}
);
}
}
Sender Component
import { Component, OnInit } from '#angular/core';
import { SerService } from '../ser.service';
import { User } from '../user';
#Component({
selector: 'app-sign-up',
templateUrl: './sign-up.component.html',
styleUrls: ['./sign-up.component.css']
})
export class SignUpComponent {
userModel = new User('', '', '', '', false);
constructor (private _service : SerService) {}
onSubmit(){
this._service.sendMessage(this.userModel.message);
}
}
I can't update the message array. How do I do this with minimal changes?

You can create a service to send data from one component to another by using BehaviourSubject
Service:
import { Injectable } from '#angular/core';
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
#Injectable({
providedIn: 'root'
})
export class DataService {
private userDetails = new BehaviorSubject<any>('');
currentUserDetails = this.userDetails.asObservable();
constructor() { }
sendUserDetails(message){
this.userDetails.next(message)
}
}
Sender Component:
import { DataService } from '/services/data.service';
export class SignupComponent implements OnInit {
public userDetails;
constructor(private _dataService: DataService) {}
ngOnInit(){
userDetails = new User('', '', '', '', false);
this._dataService.sendUserDetails(this.userDetails);
}
}
Receiver Component
import { DataService } from '/services/data.service';
export class LoginComponent implements OnInit {
public userDetails;
constructor(private _dataService: DataService) {}
ngOnInit(): void {
this._dataService.currentUserDetails.subscribe(userDetails => this.userDetails = userDetails);
}
Blockquote

Trigger function with event emitter

Is it possible to trigger a function in another component from the current component with EventEmitter, as sort of a callback? For example, after I finish the API request a success function occurs, like so:
#Output() afterAPIRequest = new EventEmitter();
handleSuccess() {
this.afterAPIRequest.emit();
}
Now, can I catch that somehow in another component and trigger another function, something like this?
// when emitted, run this
refreshListIfEmitted() {
this.refreshMyList();
}

use a service
import { Injectable } from '#angular/core';
import { Observable, Subject } from 'rxjs';
#Injectable()
export class MessageService {
private _message: Subject<any>;
constructor() {
this._message = new Subject();
}
get changes(): Observable<any> {
return this._message.asObservable();
}
set message(message: any) {
this._message.next(message);
}
}
component one
import { Component } from '#angular/core';
import { HttpClient } from '#angular/common/http';
#Component({
selector: 'app-one',
templateUrl: './one.component.html',
styleUrls: ['./one.component.scss'],
})
export class OneComponent {
constructor(private _http: HttpClient, private _message: MessageService) { }
apiRequest(): void {
this._http.get('end-point').subscribe(value => this._message.message = value);
}
}
component two
import { Component } from '#angular/core';
#Component({
selector: 'app-two',
templateUrl: './two.component.html',
styleUrls: ['./two.component.scss'],
})
export class TwoComponent {
constructor(private _message: MessageService) {
this._message.changes.subscribe(value => console.log(value));
}
}

Inject data from service to component

Currently, I'm using Rx.JS and Angular 7. My problem contains with the issue in Observable.
The problem is I can't fetch data from service to form-code.component.
After I've used setShortCode() there isset data, but in form-code.component.ts i can't see seebscribe() data
shortcode.service.ts
import { Injectable, NgZone } from '#angular/core';
import { Subject, Observable } from 'rxjs';
#Injectable({
providedIn: 'root'
})
export class ShortcodeService {
public shortcode = new Subject<any>();
constructor(private zone: NgZone) {}
setShortCode(code) {
this.zone.run(() => {
this.shortcode.next(code);
});
}
getShortCode(): Observable<any> {
return this.shortcode.asObservable();
}
}
dnd.component.ts
this.textAreaText = `<iframe src="${window.location.origin +
'/form/' +
project.id}/design" width="100%" height="500px" frameborder="0"></iframe>`;
this.shortCodeService.setShortCode(this.textAreaText);
this.router.navigate(['/form-copy']);
form-code.components.ts
import { Component, OnInit, OnDestroy, AfterViewInit } from '#angular/core';
import { ShortcodeService } from '../../services/shortcode.service';
import { DomSanitizer, SafeHtml } from '#angular/platform-browser';
import { Subscription } from 'rxjs';
#Component({
selector: 'app-form-code',
templateUrl: './form-code.component.html',
styleUrls: ['./form-code.component.scss']
})
export class FormCodeComponent implements OnInit, OnDestroy {
constructor(
private sanitizer: DomSanitizer,
private shortCodeService: ShortcodeService
) {}
shortText: string;
sub: Subscription;
ngOnInit() {
this.sub = this.shortCodeService.getShortCode().subscribe(
shortcode => {
console.log(shortcode);
this.shortText = shortcode;
},
error => console.log(error),
() => {}
);
}
ngOnDestroy(): void {
//Called once, before the instance is destroyed.
//Add 'implements OnDestroy' to the class.
this.sub.unsubscribe();
}
}

Working, When I changed Subject to BehaviorSubject

implement angular2-virtual-scroll with observable in angular4

I am trying to implement angular2-virtual-scroll in an angular4 project. Firstly, can anyone confirm if I would have a problem implementing it in NG4. I don't think I should and I haven't seen any notices to the contrary. Secondly I am using an observable instead of a promise shown in the NPM angular2-virtual-scroll docs. However, when I applied the virtual-scroll tag there is no change in my output...no scroll bar ..the data from the observable is displayed but no scrolling. The following are the relevant code segments:
Home.component.html
<h1 style="color: #76323f">
{{title}}
</h1>
<h4>
{{description}}
</h4>
<h2>Coming Soon....</h2>
<app-events-list [upcomingEvents]="upcomingEvents"></app-events-list>
home.component.ts
import {Component, OnInit,OnDestroy } from '#angular/core';
import {UpcomingEvent} from './../../interface/upcomingevent';
import {EventService} from './../../services/event.service';
import {Subscription} from 'rxjs/Subscription';
#Component({
selector: 'app-home',
templateUrl: './home.component.html',
styleUrls: ['./home.component.css']
})
export class HomeComponent implements OnInit, OnDestroy {
upcomingEvents: Array<UpcomingEvent>;
title = 'Welcome....';
description='Events promotions....';
eventServiceSub: Subscription;
constructor(private eventService: EventService){
this.upcomingEvents = [];
}
ngOnInit() {
this.eventServiceSub=this.eventService.getEvents().subscribe(upcomingEvents=>{this.upcomingEvents=upcomingEvents.slice(0,25);
});
}
ngOnDestroy(){
if (this.eventServiceSub){
this.eventServiceSub.unsubscribe();
}
}
}
event-list-component.html
<virtual-scroll [items]="items" (update)="upcomingEvents = $event"
(change)="onlistChange($event)">
<app-upcomingevent *ngFor="let upcomingEvent of upcomingEvents"[upcomingEvent]="upcomingEvent" [eventItemCss]="'event-item'"></app-upcomingevent>
<div *ngIf="loading" class="loader">Loading.....</div>
</virtual-scroll>
event-list-component.ts
import { Component, Input, OnDestroy, OnInit } from '#angular/core';
import { UpcomingEvent } from './../../interface/upcomingevent';
import { trigger,state,style,transition,animate,keyframes } from '#angular/animations';
import { ChangeEvent } from 'angular2-virtual-scroll';
import {EventService} from './../../services/event.service';
import {Subscription} from 'rxjs/Subscription';
#Component({
selector: 'app-events-list',
templateUrl: './events-list.component.html',
styleUrls: ['./events-list.component.css'],
animations: []
})
export class EventsListComponent implements OnInit, OnDestroy {
#Input()
upcomingEvents: Array<UpcomingEvent>;
items=this.upcomingEvents;
protected buffer: Array<UpcomingEvent> =[];
protected loading: boolean;
eventServiceSub: Subscription;
constructor(private eventService: EventService) {
this.upcomingEvents=[];
}
ngOnInit() {
}
ngOnDestroy(){
if (this.eventServiceSub){
this.eventServiceSub.unsubscribe();
}
}
protected onlistChange(event: ChangeEvent){
if (event.end !==this.buffer.length) return;
this.loading=true;
this.eventServiceSub=this.eventService.getEvents().subscribe(upcomingEvents=>{
this.buffer=upcomingEvents.slice(this.buffer.length,25);
this.loading=false;
}, ()=> this.loading=false);
}
}
eventService.ts
import { Injectable } from '#angular/core';
import {UpcomingEvent} from './../interface/upcomingevent'
import {Http} from '#angular/http';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/map';
#Injectable()
export class EventService {
constructor(private http: Http) { }
getEvents(): Observable<UpcomingEvent[]>
{
return this.http
.get(`https://jsonplaceholder.typicode.com/posts`)
.map(response => response.json() as UpcomingEvent[]);
}
}
upcomingEvents.html
<md-card [ngClass]="'event-item'">
<h4 [ngClass]="'event-title'" [ngStyle]="{'color':'purple'}"> {{upcomingEvent.title}}</h4>
<md-card-actions>
<button md-button>LIKE</button>
<button md-button>SHARE</button>
</md-card-actions>
</md-card>
upcomingEvents.component.ts
import { Component, Input,OnInit } from '#angular/core';
import { UpcomingEvent } from './../../interface/upcomingevent';
#Component({
selector: 'app-upcomingevent',
templateUrl: './upcomingevent.component.html',
styleUrls: ['./upcomingevent.component.css']
})
export class UpcomingeventComponent implements OnInit {
#Input()
upcomingEvent: UpcomingEvent;
#Input()
eventItemCss: string;
constructor() { }
ngOnInit() {
if (!this.upcomingEvent) {
this.upcomingEvent=<UpcomingEvent> {};
}
}
}
The way it suppose to work is that the HomeComponent request data from the eventService via an observable..the data is then passed to the eventList component where it is iterated on and pass to the upcomingEvents component to present via HTML. 25 events are requested at first and if the user scroll to the end another 25 is requested from the eventService...this time by the upcomingEvents component. I am not sure this is the most efficient way to do it but in either case it doesn't work. The virtual-scroll seems to have no effect on the output....I would really appreciate someone showing me what I am doing wrong....Thanks

I think I see a problem in your code. When using virtual-scroll you need to keep two arrays - one for all loaded data, and one for currently rendered items. Looks like you kinda mixed them up.
Let's call all-items-array as items and render-array - upcomingEvents
First chunk of items will be passed from the parent component, hence:
Home.component.html
...
<app-events-list [items]="upcomingEvents"></app-events-list>
event-list-component.html looks good
event-list-component.ts
import { Component, Input, OnDestroy, OnInit } from '#angular/core';
import { UpcomingEvent } from './../../interface/upcomingevent';
import { trigger,state,style,transition,animate,keyframes } from '#angular/animations';
import { ChangeEvent } from 'angular2-virtual-scroll';
import {EventService} from './../../services/event.service';
import {Subscription} from 'rxjs/Subscription';
#Component({
selector: 'app-events-list',
templateUrl: './events-list.component.html',
styleUrls: ['./events-list.component.css'],
animations: []
})
export class EventsListComponent implements OnInit, OnDestroy {
#Input()
items: Array<UpcomingEvent> = [];
upcomingEvents: Array<UpcomingEvent>;
protected loading: boolean;
eventServiceSub: Subscription;
constructor(private eventService: EventService) {
this.upcomingEvents=[];
}
ngOnInit() {
}
ngOnDestroy(){
if (this.eventServiceSub){
this.eventServiceSub.unsubscribe();
}
}
protected onlistChange(event: ChangeEvent){
if (event.end !==this.items.length) return;
this.loading=true;
this.eventServiceSub=this.eventService.getEvents().subscribe(upcomingEvents=>{
this.items=upcomingEvents.slice(0, this.items.length + 25);
this.loading=false;
}, ()=> this.loading=false);
}
}
warning! code not tested, I simply edited your code.

Passing value between two angular2 component typescript files

I have two components that are not parent and child components but i need to pass value from component A to component B.
example:
src/abc/cde/uij/componentA.ts has variable CustomerId = "ssss"
need to pas that variable customerID to src/abc/xyz/componentB.ts

Simple example:
Component A:
#Component({})
export class ComponentA {
constructor(private sharedService : SharedService) {}
sendMessage(msg : string) {
this.sharedService.send(msg);
}
}
Component B:
#Component({})
export class ComponentB {
constructor(private sharedService : SharedService) {
this.sharedService.stream$.subscribe(this.receiveMessage.bind(this));
}
receiveMessage(msg : string) {
console.log(msg); // your message from component A
}
}
Shared service:
#Injectable()
export class SharedService {
private _stream$ = new Rx.BehaviorSubject("");
public stream$ = this._stream$.asObservable();
send(msg : string) {
this._stream$.next(msg);
}
}
Shared service have to be placed in the same NgModule.

On your service define a setMyProperty() and a getMyProperty(). Then setMyProperty with a value from Component A. ComponentB then getMyProperty where you return the value...
You have to inject the service into both components.

You could give this a shot. Its pretty simple and straight forward.
I just followed THIS example and made some changes so that it could be siblings talking instead of parent/child.
my-service.service.ts
import { Injectable } from '#angular/core';
import { Subject } from 'rxjs/Subject';
#Injectable()
export class MyService {
// Observable string sources
private myAnnouncedSource = new Subject<string>();
// Observable string streams
myAnnounced$ = this.myAnnouncedSource.asObservable();
// Service message commands
announceItem(item: string) {
this.myAnnouncedSource.next(item);
}
}
my-comp1.component.ts
import { Component } from '#angular/core';
import { MyService } from './my-service.service';
#Component({
selector: 'my-compA',
template: `...`,
providers: [MyService]
})
export class MyComponentA {
constructor(private myService: MyService) {
}
announceToOtherComps() {
let sharedItem = "shibby";
this.myService.announceItem(sharedItem);
}
}
my-comp2.component.ts
import { Component, Input, OnDestroy } from '#angular/core';
import { MyService } from './my-service.service';
import { Subscription } from 'rxjs/Subscription';
#Component({
selector: 'my-compB',
template: `...`,
providers: [MyService]
})
export class MyComponentB implements OnDestroy {
sharedItem = '<no data>';
subscription: Subscription;
constructor(private myService: MyService) {
this.subscription = myService.myAnnounced$.subscribe(
item => {
this.sharedItem = item;
});
}
ngOnDestroy() {
// prevent memory leak when component destroyed
this.subscription.unsubscribe();
}
}

<component-a [id]="product.id"></component-a>
In the component-a ts file .Use it like below
export class ComponentA implements OnInit {
#Input() // <------------
id: number;
(...)
}