I am new to angular and trying to update variable but I variable is not updating in view. I am accessing a variable "name" created in service and updating it but it isn't working. When I call clickme() the value of variable name doesn't update on the webpage and shows old value "no name". I want to change the variable name value to "rahul" and display it on the page.
my service:
import { Injectable } from '#angular/core';
#Injectable({
providedIn: 'root'
})
export class FirstService {
name:string="no name"
setName() {
this.name="rahul"
}
}
code:
import { Component, OnInit } from '#angular/core';
import { FirstServiceService } from './first-service.service';
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css'],
providers: [FirstService]
})
export class AppComponent implements OnInit {
account:any
name:string
constructor(private userName:FirstService){ }
ngOnInit(): void {
this.name=this.userName.name
}
clickMe(e){
this.userName.setName()
}
}
You usually do with this way:
Service
import { Injectable } from '#angular/core';
#Injectable({
providedIn: 'root'
})
export class FirstService {
private name:string="no name";
setName(_name: string): void {
this.name = _name;
}
getName(): string {
return this.name;
}
}
Component
import { Component, OnInit } from '#angular/core';
import { FirstService } from './first-service.service';
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css'],
providers: [FirstService]
})
export class AppComponent implements OnInit {
account:any
name:string
constructor(private firstService: FirstService){ }
ngOnInit(): void {
this.name=this.firstService.getName();
}
clickMe(e){
this.userName.setName("rahul");
this.name=this.firstService.getName();
}
}
Whereas I must admit that the value of name normally doesn't get set by the same method that afterwards consumes it from the service. At least not when these are the only 2 lines of code in the method, though. But I reckon you're still playing around a little with services and then it's okay.
There is no need to set the same variable name in service like component.You can use anything you want.
In App component
clickMe(e){
this.name=this.userName.setName();
}
In service
getName() {
return this.name;
}
I hope it will help
You only equals the variable "name" to this.userName.name in OnInit, this is the reason because you don't see any change -you're showing the variable "name", not the variable this.usuerName.Name.
Normally you can use some simple, it's a getter
You can write in component
export class AppComponent implements OnInit {
account:any
//NOT have a variable "name", just a getter
get name(){
return this.userName.name;
}
//even if you want you can write
set name(value)
{
this.userName.name=value;
}
constructor(private userName:FirstService){ }
ngOnInit(): void {
}
clickMe(e){
this.userName.setName()
//or this.name="George"; //if you include the function set name()
//or this.userName.name="George"
}
}
Related
I have just started with Angular and have already faced an issue: a button actually toggles the variable I need (show) but it doesn't affect the course.component
course.component must show app-csgo-course, boolean show is true because the component is visible, but after it toggles in navbar.component, nothing changes.
<app-csgo-course *ngIf="show"> </app-csgo-course>
import { NavbarComponent } from './../navbar/navbar.component';
import { Component, OnInit} from '#angular/core';
import { CourseService } from 'src/app/course.service';
#Component({
selector: 'app-course',
templateUrl: './course.component.html',
styleUrls: ['./course.component.css']
})
export class CourseComponent implements OnInit {
constructor() { }
ngOnInit(): void { }
service = new CourseService;
show = this.service.GetShow();
}
In navbar.component there's a button which toggles the "show" variable
<button (click)="ToggleShow()" >
<li class="nav-item active" id="csgo-logo">
<a href="#">
<img class="game-logo" src="assets\img\csgo-logo.png" title="Counter Strike: Global Offensive">
<!-- <a>CS:GO <span class="sr-only">(current)</span></a> -->
</a>
</li>
</button>
import { CourseService } from 'src/app/cheat.service';
import { Component, OnInit, Input, Output, } from '#angular/core';
#Component({
selector: 'app-navbar',
templateUrl: './navbar.component.html',
styleUrls: ['./navbar.component.css']
})
export class NavbarComponent implements OnInit {
service = new CourseService;
show = this.service.GetShow();
ngOnInit(): void {
}
public ToggleShow() {
this.service.show = this.service.ToggleShow();
console.log(this.service.show);
return this.service.show;
}
}
The course.service file
#Injectable({
providedIn: 'root'
})
export class CourseService {
show: boolean = true;
GetShow() {
return this.show;
}
ToggleShow() {
return this.show = !this.show
}
constructor() { }
}
}
Would appreciate your help!
Since you are new to Angular, let me break it down for you.
You need to create a BehaviorSubject to capture the event of toggle (this is called reactive programming which is a achieved using RxJS in Angular ).
Do not use new for a service, rather inject it in constructor.
course.service
#Injectable({
providedIn: 'root'
})
export class CourseService {
private show: boolean = true;
private toggle$ = new BehaviorSubject<boolean>(true);
constructor() { }
toggleEvent() {
return this.toggle$.asObservable();
}
toggleShow() {
this.show = !this.show
this.toggle$.next(this.show);
}
}
in NavbarComponent
import { CourseService } from 'src/app/cheat.service';
import { Component, OnInit, Input, Output, } from '#angular/core';
#Component({
selector: 'app-navbar',
templateUrl: './navbar.component.html',
styleUrls: ['./navbar.component.css']
})
export class NavbarComponent implements OnInit {
show = boolean;
// IMP: make sure to inject the service and not do "new CourseService;"
constructor(public service: CourseService){}
ngOnInit(): void {
this.service.toggleEvent().subscribe(showFlag => {
this.show = showFlag;
})
}
public ToggleShow(): void {
this.service.toggleShow();
}
}
in courseComponent
import { Component, OnInit} from '#angular/core';
import { CourseService } from 'src/app/course.service';
#Component({
selector: 'app-course',
templateUrl: './course.component.html',
styleUrls: ['./course.component.css']
})
export class CourseComponent implements OnInit {
show: boolean ;
// IMP: make sure to inject the service and not do "new CourseService;"
constructor(public service: CourseService){}
ngOnInit(): void {
this.service.toggleEvent().subscribe(showFlag => {
this.show = showFlag;
})
}
}
PS: I would suggest you to read about "how to unsubscribe an observable" and how it causes memory leaks. Once you get some idea, you should implement that in the above provided code as well. That's a best practice. Happy learning. Let me know if you have any more questions
Angular app is compiling successfully but giving the following errors in 'ng build --prod'
ERROR in src\app\header\header.component.html(31,124): : Property 'searchText' does not exist on type 'HeaderComponent'.
src\app\dashboard\dashboard.component.html(3,72): : Property 'newsService' is private and only accessible within class 'DashboardComponent'.
src\app\dashboard\dashboard.component.html(3,72): : Property 'p' does not exist on type 'DashboardComponent'.
src\app\dashboard\dashboard.component.html(29,46): : Property 'p' does not exist on type 'DashboardComponent'.
I have used these properties in my html file as below:
header.component.htmlfile
<input type="text" class="form-control mr-2 align-self-center" required placeholder="Search" name="searchText" [ngModel]="searchText" value="">
dashboard.component.htmlfile
<pagination-controls class="text-center" (pageChange)="p = $event"></pagination-controls>
my header.component.html file
import { Component, OnInit, Output, EventEmitter, ViewEncapsulation } from '#angular/core';
import { NgForm } from '#angular/forms';
#Component({
selector: 'app-header',
templateUrl: './header.component.html',
styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
filterText : string;
#Output() search = new EventEmitter();
#Output() filterButton = new EventEmitter();
constructor() { }
ngOnInit() {
}
onSubmit(form : NgForm)
{
console.log(form);
this.search.emit(form);
}
filterClicked($event)
{
this.filterText = $event.target.text;
this.filterButton.emit(this.filterText);
}
}
my dashboard.component.html file
import { Component, OnInit, ViewEncapsulation } from '#angular/core';
import { NewsService } from '../shared/news.service';
import { NewsModel } from '../shared/news.model';
import { Form } from '#angular/forms';
import { Pipe, PipeTransform } from '#angular/core';
import { element } from 'protractor';
#Component({
selector: 'app-dashboard',
templateUrl: './dashboard.component.html',
styleUrls: ['./dashboard.component.css']
})
export class DashboardComponent implements OnInit {
articles : any;
temp : NewsModel = new NewsModel;
constructor(private newsService : NewsService) { }
ngOnInit() {
this.FetchHeadlines();
}
FetchHeadlines()
{
this.newsService.GetAllGaurdian()
.subscribe((result) =>
{
this.articles = result;
this.articles.response.results.forEach(element => {
this.newsService.newsArticles.push(this.newsService.CusotomMapper(element));
});
})
}
}
can't able to figure out where is the error exactly!
I think the error descriptions are as accurate as it can be. each of them tells you that something wrong with your component, lets examine each of them
ERROR:
ERROR in src\app\header\header.component.html(31,124): : Property 'searchText' does not exist on type 'HeaderComponent'.
you have searchText in HeaderComponent HTML, but not in the Component itself
SOLUTION: add searchText variable to the Component
#Component({
selector: 'app-header',
templateUrl: './header.component.html',
styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
searchText:string
...
}
ERROR :
src\app\dashboard\dashboard.component.html(3,72): : Property 'newsService' is private and only accessible within class 'DashboardComponent'.
all the fields you are using inside the template, must be the public field inside component itself, otherwise it will not compile
SOLUTION: change private modifier to public at newService
#Component({
selector: 'app-dashboard',
templateUrl: './dashboard.component.html',
styleUrls: ['./dashboard.component.css']
})
export class DashboardComponent implements OnInit {
constructor(public newsService : NewsService) { }
...
}
ERRORS :
src\app\dashboard\dashboard.component.html(3,72): : Property 'p' does not exist on type 'DashboardComponent'.
src\app\dashboard\dashboard.component.html(29,46): : Property 'p' does not exist on type 'DashboardComponent'.
same as HeaderComponent. you are using p field but it's not defined in DashboardComponent
SOLUTION : add p field to the dashboard component
#Component({
selector: 'app-dashboard',
templateUrl: './dashboard.component.html',
styleUrls: ['./dashboard.component.css']
})
export class DashboardComponent implements OnInit {
p:any
...
}
You are trying to access from the template, variables that aren't defined in the corresponding components.
In header.component.html you are setting [ngModel]="searchText" and variable searchText isn't defined on header.component.ts. Could it be filterText variable instead?
In dashboard.component.html you are setting p = $event and variable p isn't defined on dashboard.component.ts. You also have an error about newsService being private. If you are gonna use it in the template it must be declared public when you inyect it on the constructor. I hope this helps. If you need more help is better if you provide a Stackblitz with minimum code.
I implemented a dynamic theme switcher (with tutorial) in my angular app. It work's but when I reload website, the choice is not remembered.
I read about localStorage and i will use it but still doesn't work because I don't know how "where" I should get data from this localStorage, that the choice of the theme will be remembered when I reload the page.
I have this code:
theme.service.ts new version
import { Injectable } from '#angular/core';
import { Subject } from 'rxjs/Subject';
#Injectable()
export class ThemeService {
private _themeDark: Subject<boolean> = new Subject<boolean>();
isDarkFunction() {
let value = localStorage.getItem('isDark');
this._themeDark.next(value);
return this._themeDark.asObservable();
}
isThemeDark = this.isDarkFunction();
setDarkTheme(isThemeDark: boolean) {
this._themeDark.next(isThemeDark);
localStorage.setItem('isDark', JSON.stringify(isThemeDark));
}
}
navbar.component.html
<div class="container-fluid switcher-container">
<mat-slide-toggle [checked]="isThemeDark | async" (change)="toggleDarkTheme($event.checked)">Dark theme</mat-slide-toggle>
</div>
navbar.component.ts
import { Component, OnInit } from '#angular/core';
import { ThemeService } from '../services/theme.service';
import { Observable } from 'rxjs/Observable';
#Component({
selector: 'app-navbar',
templateUrl: './navbar.component.html',
styleUrls: ['./navbar.component.scss']
})
export class NavbarComponent implements OnInit {
isThemeDark: Observable<boolean>;
constructor(
private themeService: ThemeService) { }
ngOnInit() {
this.isThemeDark = this.themeService.isThemeDark;
}
toggleDarkTheme(checked: boolean) {
this.themeService.setDarkTheme(checked);
}
}
app.component.ts
import { Component, OnInit } from '#angular/core';
import { Observable } from "rxjs/Observable";
import { ThemeService } from "./services/theme.service";
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss'],
providers: [ThemeService]
})
export class AppComponent implements OnInit {
isThemeDark: Observable<boolean>;
constructor(
public themeService: ThemeService) {
}
ngOnInit() {
this.isThemeDark = this.themeService.isThemeDark;
}
}
Please help,
Regards
You might write something like the following in theme.service.ts.
I don't know if it will run flawlessly as is but the idea is to read from localstorage in isThemeDark().
isThemeDark() {
let value = localStorage.getItem('isDark');
this._themeDark.next(value);
return this._themeDark.asObservable();
}
I think it's because you when you do localStorage.getItem('isDark') the result is a string, not a boolean. Maybe try:
let value = JSON.parse(localStorage.getItem('isDark')) === true;
Also check manually if the localstorage is kept after a refresh. Some browsers have a setting to clear everything on refresh.
If I have a component like this:
import { Component, OnInit, ViewChild } from '#angular/core';
#Component({
selector: '...',
templateUrl: './...html',
styleUrls: ['./...scss']
})
export class TestClass implements OnInit {
testVariable : string = 'Test';
constructor() { }
ngOnInit() {}
printTest(): void{
console.log(this.testVariable);
}
}
If I call printTest method from an another component, the result will be undefined. Why? How can I figure out this?
Typo here
console.log(this.tetsVariable);
should be
console.log(this.testVariable);
So, What I am trying to do seems like it would be trivial. And it probably is. But I can't figure it out. My question is:How can I pass a variable from #Input to a service in an Angular2 component? (Code has been simplified)
My component is as follows:
import { Component, Input } from '#angular/core';
import { CMSService } from '../cms.service';
#Component({
selector: 'cmstext',
templateUrl: './cmstext.component.html',
styleUrls: ['./cmstext.component.css']
})
export class CMSTextComponent {
constructor(private cms: CMSService) { }
#Input() id : string;
content = this.cms.getContent(this.id); // this.id is NULL so content is NULL
}
And then my service:
import { Injectable } from '#angular/core';
#Injectable()
export class CMSService {
constructor() { }
getContent(textId:string) : string {
this.text = textId; // textId is NULL so this.text returns NULL
return this.text;
}
}
My component template:
<p>id: {{id}}</p>
<p>Content: {{content}}</p>
When <cmstext id="4"></cmstext> is added to another component template the output is:
id: 4
content:
I'm just diving into Angular2 any help or suggestions would be greatly appreciated!
Just make it a setter and put the code there:
#Input()
set id(value : string) {
this.content = this.cms.getContent(value);
}
As pointed out by #Kris Hollenbeck,ngOnInit() was the answer. My final code looked like this. The component now passed the variable to the service.
import { Component, Input, OnInit } from '#angular/core';
import { CMSService } from '../cms.service';
#Component({
selector: 'cmstext',
templateUrl: './cmstext.component.html',
styleUrls: ['./cmstext.component.css']
})
export class CMSTextComponent implements OnInit {
public content : string;
#Input() id : string;
constructor(private cms: CMSService) { }
ngOnInit() {
this.content = this.cms.getContent(this.id);
}
}
This assigned the data from the service to the variable "content" and the id passed from the element attribute to the variable "id". Both variables were then accessible to the template!