Having trouble setting a default value for your Angular dropdown? Looking for alternative solutions that actually work?

Objective: Customize the default value for a dropdown menu to switch between English (/en/) and Spanish (/es/) addresses on the website.

Challenge: Despite extensive research, including consulting various sources like Angular 2 Dropdown Options Default Value, none of the suggested solutions have been successful in achieving the desired outcome.

What seems to be the issue? Is it necessary to use a form/mat-form or is there a more straightforward approach available?

Approaches Tried: Below are some of the different methods attempted in both the HTML and TypeScript code:

<mat-select (selectionChange)="doSomething($event)" [value]="language"> 
<mat-select (selectionChange)="doSomething($event)" [value]="English">  
<mat-select (selectionChange)="doSomething($event)" [(ngModel)]='defaultLanguage'>

HTML Code:

<form [formGroup]="_siteForm">
      <mat-form-field class="right">
          <mat-select (selectionChange)="doSomething($event)" [(ngModel)]='defaultLanguage'>
              <mat-option *ngFor="let language of languages" [value]="language">
                  {{language.viewValue}}
              </mat-option>
          </mat-select>
      </mat-form-field>
</form>

TypeScript Code:

public _siteForm             : FormGroup;
this._siteForm = fb.group({
            'languages' : ['']
        });
public languages = [
  { value: "en", viewValue: 'English' },
  { value: "es", viewValue: 'Spanish' }
   ];

public defaultLanguage          : string = "English";

if (this.localeId == "en") { this._siteForm.controls["languages"].setValue(this.languages.filter(item => item.value === 'en')[0].viewValue); }
else { this._siteForm.controls["languages"].setValue(this.languages.filter(item => item.value === 'es')[0].viewValue); }

Another Method

this._siteForm.setValue({ languages: "en" });

Answer №1

Perhaps the issue lies in the discrepancy between the default values you are setting and the objects you are iterating through.

In one instance, the type is string:

<mat-select (selectionChange)="doSomething($event)" [value]="language"> 
<mat-select (selectionChange)="doSomething($event)" [value]="English">

While in another, it's a JSON object:

<mat-option *ngFor="let language of languages" [value]="language">
     {{language.viewValue}}
</mat-option>

To resolve this, ensure that both are of the same type - either both JSON objects or both strings.

If you opt for [value]="languages[0]", the default value will be set based on the first element in the languages array.

https://github.com/angular/components/issues/7771#issuecomment-336482394

Answer №2

Here is a suggestion for you:

const languageOptions = [
  { value: "en", viewValue: 'English' },
  { value: "es", viewValue: 'Spanish' }
   ];

const defaultLanguage = languageOptions[0]; // or languageOptions[1]

A potential issue I noticed is that you are attempting to make your ngModel, which is a string, correspond with the [value] attribute, which is an object

<mat-select (selectionChange)="doSomething($event)" [(ngModel)]='defaultLanguage'>
     <mat-option *ngFor="let language of languageOptions" [value]="language">
          {{language.viewValue}}
     </mat-option>
</mat-select>

Answer №3

To enhance your code, you could consider implementing the following:

<mat-option *ngFor="let language of languages" [value]="language.value">
    {{language.viewValue}}
</mat-option>

Afterwards, make sure to assign a default language value from the available options:

public defaultLanguage: String = "en";

This approach simplifies the options as plain strings instead of JSON objects, facilitating easy comparison. Currently, your defaultLanguage variable does not correspond to any of the provided options.

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