ngDestroy lifecycle method is not triggering for dynamically created component.
I'm creating multiple component dynamically using ComponentFactoryResolver.
In my dynamically created component I'm fetching some data from API and I'm periodically fetching the data for every 5 mins using setInterval method. and I'm clearing the Interval instance inside ngDestroy method , while redirecting to different page, the component's ngDestroy is not triggering and the API is triggering even the component is not in the view.
This is how I'm creating components dynamically.
const factory = this.resolver.resolveComponentFactory(DynamicComponent); // Component Construction
const ref = factory.create(this.injector);
Here is my DynamicComponent which has the functionalities
import { Component, OnInit, OnDestroy } from "#angular/core";
#Component({
selector: "app-dynamic,
templateUrl: "./dynamic.component.html",
styleUrls: ["./dynamic.component.scss"]
})
export class DynamicComponent implements OnInit, OnDestroy {
loopCount: number;
autoRefreshInterval: any;
constructor() {}
ngOnInit() {
this.fetchData();
this.startAutoRefreshLoop();
}
ngOnDestroy(): void {
console.log("Destroying loop"); // ngOnDestroy is not triggering
this.clearAutoRefreshLoop();
}
clearAutoRefreshLoop() {
clearInterval(this.autoRefreshInterval);
}
/*
function for starting the Automatically recall the service for certain period of time
*/
startAutoRefreshLoop() {
console.log("starting loop");
this.loopCount = 10 * 1000;
this.autoRefreshInterval = setInterval(() => {
this.fetchData();
}, this.loopCount);
}
fetchData() {
// FETCHING DATA FROM API CODE ....
}
}
You need to destroy the dynamically loaded component by manually calling : this.componentRef.destroy(); to trigger ngOndestroy()
Example :
import {
Component,
ViewChild,
ViewContainerRef,
ComponentFactoryResolver,
ComponentRef,
ComponentFactory
} from '#angular/core';
import { DynamicComponent } from './dynamic.component';
#Component({
selector: 'app-root',
templateUrl: './app.component.html'
})
export class AppComponent {
title = 'app';
componentRef: any;
#ViewChild('container', { read: ViewContainerRef }) entry: ViewContainerRef;
constructor(private resolver: ComponentFactoryResolver) { }
createComponent(message) {
this.entry.clear();
const factory = this.resolver.resolveComponentFactory(DynamicComponent);
this.componentRef = this.entry.createComponent(factory);
}
destroyComponent() {
this.componentRef.destroy(); // you need to call this
}
}
For more information : how-to-dynamically-create-a-component-in-angular
Related
I have a problem with reloading my child component from parent component in Angular.
Here is an example of what I want to do.
This is my child component
import { Component } from "#angular/core";
#Component({
selector: "app-child",
template: `<p> {{ticks}} </p>`,
styleUrls: ["./child.component.css"]
})
export class ChildComponent {
ticks = Date.now().valueOf();
constructor() {}
update(): void {
this.ticks = Date.now().valueOf();
}
}
And here is my parent component:
import { Component, OnInit, ViewChild } from '#angular/core';
import { ChildComponent } from './../child/child.component';
#Component({
selector: 'app-parent',
templateUrl: './parent.component.html',
styleUrls: ['./parent.component.css'],
})
export class ParentComponent implements OnInit {
#ViewChild(ChildComponent, { static: false }) childC: ChildComponent;
showChild: boolean = true;
constructor() {}
ngOnInit() {}
onUpdateChild() {
this.childC.update();
}
}
Parent Component HTML :
<p>
parent works!
<button (click)="onUpdateChild()">update</button>
<app-child *ngIf="showChild"></app-child>
<app-child *ngIf="showChild"></app-child>
</p>
The main problem is that if I use my child component multiple time, and trying to click on “update” button, it just updates one of my child component that is used in parent component, but I want to update all same child component in parent component, here is what happens when you click on “update” button, only first value will change, not both.
How can I fix it ?!?
You can use #ViewChildren and QueryList to do what you are looking for.
#ViewChildren(ChildComponent) childrenC!: QueryList<ChildComponent>;
And your function would look like:
onUpdateChild() { //I would rename it to onUpdateChildren
if(this.childrenC) {
this.childrenC.forEach((childC: ChildComponent) => {
this.childC.update();
});
}
}
If you wanted your child component to update on it's own - as stated by a comment to your original post - this is an example of what you could do so you wouldn't even need the update button:
import { Component, OnInit } from "#angular/core";
#Component({
selector: "app-child",
template: `<p> {{ticks}} </p>`,
styleUrls: ["./child.component.css"]
})
export class ChildComponent implements OnInit {
ticks = Date.now().valueOf();
constructor() {}
ngOnInit(): void {
setInterval(() => {
this.ticks = Date.now().valueOf();
}, 1000); //updates every 1 second
}
}
Another option you can do without using a button is to use #Input with the ticks property that updates the value from the parent through an input.
I defined a property here in my function
evs: string
...
openArticle(url){
this.evs = url
console.log(this.evs)
this.navCtrl.navigateForward('/url-page')
}
And I a trying to pass the value of 'this.evs' to another ts file and use its value but I do not know how to do this. I tried exporting it like this.
export const webpage = this.evs
but this.evs has no value until someone performs the openArticle function ad so I keep getting the error. "Cannot read property 'evs' of undefined"
What i need to do is tranfer the variable to the 'url-page' page and use the value of this.evs only after the openArticle function has bee called. How do I go about this?
As per my understanding you are trying to share data between two components.
So choose one of them as per your requirements.
Parent to Child: Sharing Data via Input().
Child to Parent: Sharing Data via Output() and EventEmitter.
Unrelated Components: Sharing Data with a Service.
This link will be helpful.
If the components have a parent/child relationship, You can share data between them via #Inpput() and #Output() decorators.
Sharing data from Parent to Child using #Input() :
<h3>Parent Component</h3>
<label>Parent Component</label>c
<input type="number" [(ngModel)]='parentValue'/>
<p>Value of child component is: </p>
<app-child [value]='parentValue'></app-child>
And in the child component, the 'parentValue' can be received as :
import { Component, OnInit, Input } from '#angular/core';
#Component({
selector: 'app-child',
templateUrl: './child.component.html',
styleUrls: ['./child.component.css']
})
export class ChildComponent implements OnInit {
#Input() value: number;
constructor() { }
ngOnInit() {
}
}
Now, in the case of sending data from Child to Parent, we can use an #Output() event emitter. So the parent would have a function to receive the emitted data from child as :
parent-app.component.html
<app-child [value]="parentValue" (childEvent)="childEvent($event)"></app-child>
parent-app.component.ts
childEvent(event) {
console.log(event);
}
And, the child.component.ts would look like :
import { Component, OnInit, Input, Output, EventEmitter } from '#angular/core';
#Component({
selector: 'app-child',
templateUrl: './child.component.html',
styleUrls: ['./child.component.css']
})
export class ChildComponent implements OnInit {
#Input() PData: number;
#Output() childEvent = new EventEmitter();
constructor() { }
onChange(value) {
this.childEvent.emit(value);
}
ngOnInit() {
}
}
If the components do not have a parent/child relationship, a shared service can be used, say, SharedService which has a BehavioralSubject, that emits value from either component, and the other component can then catch the changed value.
Eg:
import { Injectable } from '#angular/core';
import { BehaviorSubject } from "rxjs/BehaviorSubject";
#Injectable()
export class SharedService {
comp1Val: string;
_comp1ValueBS = new BehaviorSubject<string>('');
comp2Val: string;
_comp2ValueBS = new BehaviorSubject<string>('');
constructor() {
this.comp1Val;
this.comp2Val;
this._comp1ValueBS.next(this.comp1Val);
this._comp2ValueBS.next(this.comp2Val);
}
updateComp1Val(val) {
this.comp1Val = val;
this._comp1ValueBS.next(this.comp1Val);
}
updateComp2Val(val) {
this.comp2Val = val;
this._comp2ValueBS.next(this.comp2Val);
}
And component1 as follows :
import { Injectable } from '#angular/core';
import { BehaviorSubject } from "rxjs/BehaviorSubject";
#Injectable()
export class SharedService {
comp1Val: string;
_comp1ValueBS = new BehaviorSubject<string>('');
comp2Val: string;
_comp2ValueBS = new BehaviorSubject<string>('');
constructor() {
this.comp1Val;
this.comp2Val;
this._comp1ValueBS.next(this.comp1Val);
this._comp2ValueBS.next(this.comp2Val);
}
updateComp1Val(val) {
this.comp1Val = val;
this._comp1ValueBS.next(this.comp1Val);
}
updateComp2Val(val) {
this.comp2Val = val;
this._comp2ValueBS.next(this.comp2Val);
}
Component 2 :
import { Component, AfterContentChecked } from '#angular/core';
import { SharedService } from "../../common/shared.service";
#Component({
selector: 'app-component2',
templateUrl: './component2.component.html',
styleUrls: ['./component2.component.css']
})
export class Component2Component implements AfterContentChecked {
comp1Val: string;
comp2Val: string;
constructor(private sharedService: SharedService) {
this.sharedService.comp2Val = "Component 2 initial value";
}
ngAfterContentChecked() {
this.comp1Val = this.sharedService.comp1Val;
}
addValue(str) {
this.sharedService.updateComp2Val(str);
}
}
You can find more on different types of subjects here
I am writing a simple counter. It has start,stop, toggle functionality in parent (app) and displaying changed value in child (counter) component using ChangeDetectionStrategy.OnPush.
Issue I am facing is not able to display initial counter value in child component on load.
Below are screenshot and code.
app.component.ts
import { Component } from '#angular/core';
import {BehaviorSubject} from 'rxjs';
#Component({
selector: 'app-root',
template: `<h1>Change Detection</h1>
<button (click)="start()">Start</button>
<button (click)="stop()">Stop</button>
<button (click)="toggleCD()">Toggle CD</button>
<hr>
<counter [data]="data$" [notifier]="notifier$"></counter>`,
})
export class AppComponent {
_counter = 0;
_interval;
_cdEnabled = false;
data$ = new BehaviorSubject({counter: 0});
notifier$ = new BehaviorSubject(false);
start() {
if (!this._interval) {
this._interval = setInterval((() => {
this.data$.next({counter: ++this._counter});
}), 10);
}
}
stop() {
clearInterval(this._interval);
this._interval = null;
}
toggleCD(){
this._cdEnabled = !this._cdEnabled;
this.notifier$.next(this._cdEnabled);
}
}
counter.component.ts
import {Component, Input, ChangeDetectionStrategy, OnInit, ChangeDetectorRef} from '#angular/core';
import {Observable} from 'rxjs/index';
#Component({
selector: 'counter',
template: `Items: {{_data.counter}}`,
changeDetection: ChangeDetectionStrategy.OnPush
})
export class CounterComponent implements OnInit {
#Input() data: Observable<any>;
#Input() notifier: Observable<boolean>;
_data: any;
constructor(private cd: ChangeDetectorRef) {}
ngOnInit() {
this.data.subscribe((value) => {
/**
Below this._data.counter is showing 0 in console.log but
not in template
**/
this._data = value;
this.cd.markForCheck();
});
this.cd.detach();
this.notifier.subscribe((value) => {
if (value) {
this.cd.reattach();
} else {
this.cd.detach();
}
});
}
}
I'm using Angular 6.1.0
your AppComponent data$ is a BehaviorSubject, which you have given an initial value. your CounterComponent data expects an Observable, which you subscribe to. The defaulted BehaviorSubject does not fire until it changes. to get the value you have to query it upon load:
#Input() data: BehaviorSubject<any>;
ngOnInit() {
this._data = this.data.value; // get the initial value from the subject
this.data.subscribe((value) => {
this._data = value;
this.cd.markForCheck();
}
);
should do the trick.
When a method is called from a child component, the Propos of parent component are not changed in angular.io.
I have this method in dashboard.component:
listPeers(){
this.loading = true;
this.localStorage.getItem("payload").subscribe( (storage : string) =>{
this.jwt = storage;
this.userService.listPeers(this.jwt).subscribe( (res) => {
this.loading = false;
if(res.success){
console.log(res.peers)
this.peers = res.peers;
this.listUsersCrm();
}else{
this.snackBar.openFromComponent(ToastComponent, {
data: res.msg
});
this.router.navigate(['/notfound']);
}
})
})
}
And on "commit-changes.component" I call this method:
import { Component, OnInit} from '#angular/core';
import { DashboardComponent } from "../dashboard/dashboard.component";
#Component({
providers: [DashboardComponent],
selector: 'app-commit-changes',
templateUrl: './commit-changes.component.html',
styleUrls: ['./commit-changes.component.scss']
})
export class CommitChangesComponent implements OnInit {
constructor(private dashBoardComponent : DashboardComponent) { }
ngOnInit() {
}
discardChanges(){
this.dashBoardComponent.listPeers();
}
}
This method is already called, but the props from parent (dashboard.component) are not changed.
Note: The method listPeers is calling API to list peers stored on BD and set peers props.
this.peers = res.peers;
What's the correctly way to executed this method and apply changes of props?
I have the following scenario in my Angular app:
A component MainDashboardComponent that is visible when I have the route /. Obviously I have the <router-outlet> tag in my app.component.html file, which looks like this:
<app-side-menu></app-side-menu>
<div class="main-container">
<div class="content">
<router-outlet></router-outlet>
</div>
</div>
As you can see I have a SideMenuComponent I use to have a side menu on all my routes. In MainDashboardComponent I have a method that for some reason needs to toggle a chat element that is situated on the side menu.
Inside the SideMenuComponent I have a method that handles the visibility toggle for the chat element and it works as expected. How can I call this method from my MainDashboardComponent and toggle the chat element from there?
What I tried with no success
I tried to inject the SideMenuComponent inside my MainDashboardComponent but, though the method toggleChat() is called, the element doesn't change it's visibility. Looks like I have a kind of multiple instance of the same component I guess...
Can you please help me with this? Thank you!
MainDashboardComponent
import { Component, OnInit } from '#angular/core';
#Component({
selector: 'app-main-dashboard',
templateUrl: './main-dashboard.component.html',
styleUrls: ['./main-dashboard.component.scss']
})
export class MainDashboardComponent implements OnInit {
constructor() { }
ngOnInit() {}
setFocus(id) {
// here I'd like to call SideMenuComponent togglechat() ...
}
}
SideMenuComponent
import { Component, OnInit } from '#angular/core';
#Component({
selector: 'app-side-menu',
templateUrl: './side-menu.component.html',
styleUrls: ['./side-menu.component.scss']
})
export class SideMenuComponent implements OnInit {
showChat: boolean;
constructor() {
this.showChat = false;
}
ngOnInit() {
}
toggleChat() {
this.showChat = !this.showChat;
}
}
To communicate between different components, there are different ways.
If you want to communicate between parent and child component, you can use EventEmitter to emit event from child component and handle the event in your parent component
If you want to communicate between any components, you can use Service and implement communication with the help of EventEmitter or Subject/BehaviorSubject
In your case, we can create a service, myService.ts and declare and eventEmitter
.service.ts
#Injectable()
export class AppCommonService {
toggle : EventEmitter<boolean> = new EventEmitter<boolean>()
}
mainDashboard.component.ts
constructor(private myService : myService){}
chatStatus : boolean = false;
ngOnInit(){
this.myService.toggle.subscribe(status=>this.chatStatus = status);
}
toggleChat(){
this.myService.toggle.emit(!this.chatStatus);
}
sideMenu.component.ts
constructor(private myService : myService){}
chatStatus : boolean = false;
ngOnInit(){
this.myService.toggle.subscribe(status=>this.chatStatus = status);
}
Generally this is the domain of a service!
Just create a service and add the "showCat" property.
Inject the service into both components
Alter SideMenuComponent to:
toggleChat() {
this.myService.showChat = !this.myService.showChat;
}
Alter MainDashboardComponent, also use this.myService.showChat to show / hide your chat window
Service TS
#Injectable()
export class MyService{
showCat:boolean = true
}
MainDashboardComponent
toggleChat() {
this.myService.showChat = !this.myService.showChat;
}
SideMenuComponent
chatVisiblity = this.myService.showCat //<-- bind this to the element attribute
You could efficiently use child to parent communication in this scenario. You'll need to create a custom event using angular's EventEmitter in your SideMenuComponent and use it in your MainDashboardComponent.
So, here is some code that may help you -
// SideMenuComponent
import { Component, OnInit } from '#angular/core';
#Component({
selector: 'app-side-menu',
templateUrl: './side-menu.component.html',
styleUrls: ['./side-menu.component.scss']
})
export class SideMenuComponent implements OnInit {
#Output() valueChange = new EventEmitter();
showChat: boolean;
constructor() {
this.showChat = false;
}
ngOnInit() {
}
toggleChat() {
this.showChat = !this.showChat;
this.valueChange.emit(this.showChat);
}
}
// MainDashboardComponent
import { Component, OnInit } from '#angular/core';
#Component({
selector: 'app-main-dashboard',
template: `<app-side-menu (valueChange)='setFocus($event)'></app-side-menu>`
styleUrls: ['./main-dashboard.component.scss']
})
export class MainDashboardComponent implements OnInit {
constructor() { }
ngOnInit() { }
setFocus(event) {
// check for required input value
console.log(event);
}
}
Refer these tutorials if required -
https://dzone.com/articles/understanding-output-and-eventemitter-in-angular,
https://angular-2-training-book.rangle.io/handout/components/app_structure/responding_to_component_events.html