Why does ngmodelChange event not fire when component loads on a dropdown? - javascript

In my Angular 8 component, I have added bi-directional binding to a dropdown control.
The view
<select (ngModelChange)='termSelectChanged($event)' [ngModel]="selected">
<option [ngValue]="t" *ngFor='let t of termsColl'>{{t?.code}}</option>
</select>
The component code
export class AppComponent implements OnInit{
public termsColl : Array<DDModel>;
public selected : DDModel;
constructor( private s : DDService ){}
termSelectChanged( event ){
alert('HIT');
}
ngOnInit(){
//service call #1
this.s.getDataForComplexBind().subscribe( data => {
this.termsColl = data;
}, error => error );
//service call #2
this.s.getOtherData( ).subscribe( data => {
//model changes here
this.selected = this.termsColl[1];
}, error => { console.error(error); });
}
}
When the component loads, it executes ngOnInit() and sets the model-bound property Selected with the first element of the array termsColl. termsColl has data but the line this.selected = this.termsColl[1]; does not change the selected option to the first element in the dropdown. In fact, when the component loads, I was expecting it to fire the event ngModelChange but it did NOT fire the event either. I have added an alert() in the code but it did not show when the component loads. It shows only if I select an option from the dropdown. How do I change the code so it will execute the ngModelChange event when the component loads?
Here is my stackblitz
https://stackblitz.com/edit/angular-version-yeg27j?file=src%2Fapp%2Fapp.component.ts

I changed the ngModeChange input to DDModel and called your termSelectChanged() from inside the subscribe. I also changed [ngModel] to [(ngModel)]
<select (ngModelChange)='termSelectChanged($event)' [(ngModel)]="selected">
<option [ngValue]="t" *ngFor='let t of termsColl'>{{t?.code}}</option>
</select>
termSelectChanged(selection: DDModel) {
console.log("HIT", selection);
}
ngOnInit() {
this.s.getOtherData().subscribe(
data => {
this.termsColl = data;
this.selected = this.termsColl[0];
this.termSelectChanged(this.selected);
},
error => {
console.error(error);
}
);
}
I can't tell you why changing this.selected from code does not trigger the ngModelChange. Maybe it's because ngModelChange is called in the template.

You can use viewToModelUpdate() of ngModel to update the value and if you want to trigger the ngModelChange. You can find more about it here.
But you need to do the following changes.
In html template:
<select (ngModelChange)='termSelectChanged($event)' [ngModel]="selected" #ngModel="ngModel">
<option [value]="t" *ngFor='let t of termsColl'>{{t?.code}}</option>
</select>
You can see I am adding a reference to the ngModel in template, which I will use it in the component class.
In the component class:
export class AppComponent {
name = "Angular 6";
version = VERSION.full;
public termsColl: Array<DDModel>;
public selected: string;
#ViewChild("ngModel") ngModel: NgModel;
constructor(private s: DDService) {}
termSelectChanged(event) {
this.selected = event;
}
ngOnInit() {
this.s.getOtherData().subscribe(
data => {
this.termsColl = data;
this.ngModel.viewToModelUpdate(this.termsColl[1]);
},
error => {
console.error(error);
}
);
}
}
You can see I am using the ngModel reference to call the viewToModelUpdate with the value, which in return triggers the ngModelChange.
Since you are not using two way binding directly, you have to set the value to the selected variable inside the trigger function termSelectChanged.
Hope this would help you to achieve your requirement.

You can use value instead of ngValue in you option elements. And assign t.code instead of t to the value attribute.
<select (ngModelChange)='termSelectChanged($event)' [ngModel]="selected">
<option [value]="t.code" *ngFor='let t of termsColl'>{{t?.code}}</option>
</select>
Reference: https://angular-version-xkjuff.stackblitz.io

termsColl has data but the code line this.selected = this.termsColl[1]; does not change the selected option to the first element in the drop down.
Because you are using propery binding [ngModel]="selected", not two-way data binding.
[(ngModel)]="selected" is for two-way binding, and the syntax is compound from:
[ngModel]="selected" and (ngModelChange)="selected = $event"
Also, the value of selected should be the value which is available in dropdown, i.e
ngOnInit(){
this.selected = this.termsColl[1].code
}
Below code would work for you:
<select [(ngModel)]="selected" (change)="onSelection()">
<option *ngFor='let t of termsColl' [value]="t.code" [selected]="selected === t.code">{{t?.code}}</option>
</select>
You might also want to refer this https://stackoverflow.com/a/63192748/13596406

Related

Select selected option not working for some reason =/

[For some reason the selected select option not showing any value just a blank area only when clicking it it shows the values. ive checked the css files and it seems fine no idea what causes the problem when i remove the [(ngModel)] it works but not getting the values =/
import { Component, OnInit } from '#angular/core';
import { Company } from '../_models/company';
import { CompanyService } from '../_services/company.service';
import { AlertifyService } from '../_services/alertify.service';
#Component({
selector: 'app-company',
templateUrl: './companies.component.html',
styleUrls: ['./companies.component.css']
})
export class CompaniesComponent implements OnInit {
selectedCompany: Company;
companies: Company[];
constructor(private companyService: CompanyService, private alertify: AlertifyService) { }
ngOnInit() {
this.loadCompanies();
}
async loadCompanies() {
this.companyService.getCompanies().subscribe((companies: Company[]) => {
this.companies = companies;
}, error => {
this.alertify.error(error);
});
}
// selectedChangeHandler(event: any) {
// this.selectedCompany = event.target.value;
// }
}
<ng-container *ngIf="companies">
<div class="col-12 col-md-3 col-xl-2 mt-5 bd-sidebar">
<label for="">Select Company</label>
<select class="form-control" [(ngModel)]="selectedCompany" >
<option selected> -- select an option -- </option>
<option *ngFor="let value of companies" [ngValue]="value">{{value.name}}</option>
</select>
</div>
</ng-container>
<!--Just a test--->
<!-- <select class="form-control col-lg-8" #selectedValue name="selectedValue" id="selectedValue" [(ngModel)]="company" (ngModelChange)="assignCorporationToManage($event)">
<option *ngFor="let value of companies" [ngValue]="company">{{value.name}}</option>
</select> -->
<ul *ngIf="selectedCompany" class="list-group list-group-flush">
<li class="list-group-item">Company name: {{selectedCompany.name}}</li>
<li class="list-group-item">Company address: {{selectedCompany.address}}</li>
<li class="list-group-item">Company estimated revenue: {{selectedCompany.estimatedRevenue}}₪</li>
</ul>
I see several issues with your example, so I am going to offer another approach, and explain what I am doing along the way.
In an Angular application, when using two way binding with [(ngModel)] on a select, the initially selected option will always be set to the one that matches the value of ngModel.
In your example, the initial value for selectedCompany is never set, and that is the reason your initial page load displays the menu with nothing selected. You are going to need to set a value onto all of your options, including the first to get this to work.
Now, since you did not provide the structure of your model titled Company, I am going to improvise and assume it contains two elements, name and value. So just remember, you will need to adjust what I have below to match the actual structure of your data.
First, on the option tags in your select in the template, id suggest using the value attribute which we will be populating with strings, instead of ngValue which is can be used to contain an object or a string. You can obtain the object that contains all of the data you need via the change event later.
Let's adjust your template file as follows:
<select class="form-control" [(ngModel)]="selectedCompany" (change)="companyChange($event.target.value)">
<option [value]="'init'">-- select a company --</option>
<option *ngFor="let company of companies" [value]="company.value">{{company.name}}</option>
</select>
Next, in your component file, lets change that property that we're using for two way binding on your select to be typed as a string:
selectedCompany:string;
Next, lets create a new property typed to your model which we will ultimately set to the company selected:
myCompany:Company;
Next, set the initially selected option in your component so that '-- select a company --' will display as the initially selected option:
ngOnInit() {
this.selectedCompany = 'init';
this.loadCompanies();
}
And lastly, inside the change event, you can use the find() method to obtain the complete set of data that you need:
companyChange(value) {
this.myCompany = this.companies.find(element => element.value === value);
console.log("User selected the company:", this.myCompany);
}

How to pre-populate ngselect in Angular?

I am grabbing some items through a http call and then want to pre-populate the ngselect, but using the abstractcontrol.setvalue() method does not seem to work.
Template Code
<ng-select [items]="cars"
bindValue="code"
bindLabel="displayName"
formControlName="car"
[clearable]="false"
[searchable]="false"
id="car"
placeholder="Select a car">
Component Code
this.setValueForPrePopulatedPlanningDetail('car', car);
private setDefaultValue(fieldName: string, value: any) {
if (value && value.length > 0) {
const field = this.myFormGroup.get(fieldName);
field.markAsDirty();
field.setValue(value);
}
}
You need set your result to the list (countries) and then use setvalue to choose the option
Set result to your list in your component:
this.countries = ['XPTO','XPTO2','XPTO3']
Define the following in your html:
<select>
<option [value]="country" *ngFor="let country of countries"> {{country}}</option>
</select>
The right way of using ng-select, would be to assign the values to the items input binding.
For instance,
<ng-select [items]="cities2"
bindLabel="name"
bindValue="id"
[multiple]="true"
placeholder="Select cities"
[(ngModel)]="selectedCityIds">
</ng-select>
And on your component.ts, you will populate ng-select options by subscribing to the observable returned by the HTTP request, and assigning it the cities2 property.
cities2: any[] = [];
ngOnInit() {
this.dataService.getData.subscribe(res => {
this.cities2 = res;
});
}
This demo might not directly answer your queries, but it shows how the various input bindings (such as items) work with ng-select.

aurelia.js print a value in my DOM from a select

my values are been printing in a alert, but how can I print this value in my DOM? like in a h1 tag?
app.html:
<template>
<select value.bind="changedValue" change.delegate="DropdownChanged(changedValue)">
<option model.bind="1">1</option>
<option model.bind="2">2</option>
<option model.bind="3">3</option>
<option model.bind="4">4</option>
</select>
</template>
app.js
export class App {
changedValue;
DropdownChanged(changedVal) {
alert(changedVal);
}
}
https://gist.run/?id=87f6897928feb504dad638d439caf92f
Your changedValue in App holds the model you select as I see it.
You just need to give it a default (and maybe a better name)
export class App {
value = 1;
Then update it when a different value is selected instead of alerting.
DropdownChanged(changedVal) {
this.value = changedVal;
}
Then you can freely use it in your template
<template>
<h1>${value}</h1>
...
As suggested, you might not need the change interceptor at all, in which case you can just bind to the select's model:
<select value.bind="selectedValue">
and
<h1>Selected Value: ${selectedValue}</h1>
(no need for any js code in this particular simplified example)

Angular2 trigger ngModelChange automatically

So I have the following code:
<div class="form-group">
<label for="backings_select">Backing Single</label>
<select class="form-control"
required
[(ngModel)]="selectedBacking"
name="backings_select"
(ngModelChange)="storeValueRedux($event, count)">
<option *ngFor="let backing of backings" [ngValue]="backing.id" [selected]="backings.length === 1">{{backing.name}}</option>
</select>
It populates a select box with results from a service call, if the array length is 1, it auto selects the only option available, this works fine.
However, by default the select box uses a value from the component as its default value.
So when the service call is made, if the array only has a length of one, the value of the model is changing, but because its being auto selected (not by user input) the storeValueRedux event is not firing.
However, if the array has more than one entry, and then is selected by a user, the function is called and works as required. Is there anyway to trigger ngModelChange in the instance that backings.length = 1?
You can't use a condition inside your method calls in HTML but you can use change and handle the condition inside your method as below
<select class="form-control"
required
[(ngModel)]="selectedBacking"
name="backings_select"
(change)="storeValueRedux($event, count)">
<option *ngFor="let backing of backings" [ngValue]="backing.id"
[selected]="backings.length === 1">{{backing.name}}</option>
selectedBacking:any{};
backings:any[]=[
{id:1, name:'a'},
{id:2, name:'a'}
]
storeValueRedux(a,b){
if(this.backings.length!=1){
console.log(this.selectedBacking);
console.log(a,b);
}
}
LIVEDEMO
The service that returned my backings was an observable, so I modified the subscribe from:
.subscribe(
results => {this.backings = results},
error => console.log(error),
);
to:
.subscribe(
results => {this.backings = results, this.testBackingLength()},
error => console.log(error),
);
And then added:
testBackingLength(){
/* If the length of the arrau is only one, the template auto selects it
and does not trigger ngOnChange, so we need to manually trigger it here,
this function is called from the subscribe a few lines up */
if (this.backings.length === 1) {
this.storeValueRedux(this.backings[0]['id'], this.count)}
}
So each time my service is called, it tests the length of the array. If the length of the array is 1, it will auto call my function.

Set selected value of select menus

I have three select menu that bind to each other and want to set selected value of two select menus. Value that I want to set comes with scope. I try ng-init but that didn't work. Working Plunker
<select ng-init="selManga=direk" ng-model="selManga" ng-options="manga.seri for manga in mangas">
<option value="">Select a Manga</option>
</select>
<select ng-init="selChapter=bacanak" ng-show="selManga" class="browser-default" ng-model="selChapter" ng-options="+idx as chapter.klasor for (idx, chapter) in selManga.randomword">
<option value="">Chapter</option>
</select>
<select ng-show="selManga.randomword[selChapter].yol" class="browser-default" ng-model="selPage" ng-options="+idx as (+idx + 1) for (idx, page) in selManga.randomword[selChapter].yol">
<option value="">Page</option>
</select>
Javascript:
.controller('nbgCtrl',function ($scope, MMG, $stateParams) {
$scope.direk = $stateParams.seri;
$scope.bacanak = $stateParams.klasor;
MMG.adlar.success(function(loHemen) {
$scope.mangas = loHemen;
});
$scope.next = function (manga, chapter, page) {
var nextPage = page + 1;
if (angular.isDefined(manga.randomword[chapter].yol[nextPage])) {
$scope.selPage = nextPage;
} else if (angular.isDefined(manga.randomword[chapter + 1])) {
$scope.selChapter = chapter + 1;
$scope.selPage = 0;
}
}
})
To extract the values for the manga,chapter and page from the url you should use the $routeParams object, which your module should include ngRoute.
I've prepared an example here it might not be obvious but if you download the code and run it in your own browser you can access routes like Manga/Naruto/ch/100 from the url bar.
Once you've restructured your application to use routes and routeParams, in my example I directly bind the chapter and page I get from the url to the view but if you bind them to the models of your dropdowns the dropdowns will update.
$scope.params = $routeParams;
$scope.selManga = $scope.params.bookId
This does not update the url as you select from the dropdown.
In your code you have assign direk and bacanak value more than one times which can cause issue. Set variable property only once.
$scope.direk = $stateParams.seri;
$scope.bacanak = $stateParams.klasor;
$scope.direk = $stateParams.xy; //Remove if not required
$scope.bacanak = $stateParams.xz; //Remove if not required
Set selManga value from $stateParams instead of setting it to direk
$scope.selManga = $stateParams.seri; // Set selManga from $stateParams
$scope.selChapter = $stateParams.klasor; // Set selChapter from $stateParams
The reason why ng-init="selManga=direk" not work is because Syntax error: ng-init="selManga=direk" should be ng-init="selManga='direk'" but after making syntax correct, dropdown will not set because of ng-repeat. ng-init set value to model but at time of setting value ng-repeat doesn't complete setting value for options so selManga set from ng-init not update option to dropdown.

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