In the event that the debugger indicates a true condition but the program fails to enter the corresponding code

Objective: Trigger the IF block when a user selects a value from the dropdown menu

Challenge: Despite the debugger indicating that the value is true, the conditional block is not being executed. Could this issue be related to any changes in the HTML code? There were some minor adjustments made to the nesting structure for better page layout, but everything else remains unchanged.

Attempted Solutions:

Examining the HTML structure

Utilizing Chrome's debugger tool

Commenting out all lines except for a console.log statement

HTML Code:

<form [formGroup]="_siteForm">
    <div class="title-container">
        <mat-card-title class="text-center" i18n="@@MoVeSeLo_H1_1">
            Please Sign In
        </mat-card-title>

        <mat-form-field class="language-field">
            <mat-select (selectionChange)="doSomething($event)" [value]="languages[i]">
                <mat-option *ngFor="let language of languages" [value]="language">
                    {{language.viewValue}}
                </mat-option>
            </mat-select>
        </mat-form-field>
    </div>
</form>

TypeScript Code:

//Array for dropdown
public languages = [
    { value: "en", viewValue: 'English' },
    { value: "es", viewValue: 'Spanish' }
     ];

//Sets default value for dropdown
if (this.localeId == "en" || this.localeId == "en-US") { this.i = 0; }
else { this.i = 1; }

//Event handler when a user selects an option from the dropdown
doSomething(event) {
        console.log("in doSomething()");
        //if value selected is Spanish
        if (event.value == "es") {
            console.log("event.value == ES");
        }
        else if (event.value == "en") { console.log("event.value == EN"); }

    }

Debugger Output (Focus on the event object):

value: "es"

viewValue: "Spanish"

If the value of event.value is "es," why is the IF block being bypassed and the console log statement not being displayed?

Answer №1

Your code isn't functioning because you're passing $event to the function, so the currently selected value (i.e., language object) can be retrieved by:

event.value -- returns {value: "en", viewValue: "English"}

Solution 1:

If you want to access the selected value from the object, you should use:

event.value.value -- returns "en"

Solution 2:

Modify:

<mat-option *ngFor="let language of languages" [value]="language">

To:

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

With this adjustment, your current code will work correctly!

Solution 3:

You can utilize the click event on the mat-option to pass the language object to the doSomething() method:

<mat-form-field class="language-field">
    <mat-select>
        <mat-option *ngFor="let language of languages" (click)="doSomething(language)" [value]="language">
            {{language.viewValue}}
        </mat-option>
    </mat-select>
</mat-form-field>

EDIT:

To set a default value, you can employ the [compareWith] @Input() property of the control for the mat-select component:

Add the following function in the TS file:

defaultValue: any = { value: "es", viewValue: "Spanish" };  // your selected value object

compareValues(obj: any, targetObj: any) {
  if (obj.value == targetObj.value) {
    return true;
  } else {
    return false;
  }
}

HTML Modification:

  • Include [(ngModel)] with the selected value
  • Add the [compareWith] function
<mat-form-field class="language-field">
    <mat-select (selectionChange)="doSomething($event)" [compareWith]="compareValues" [(ngModel)]="defaultValue">
        <mat-option *ngFor="let language of languages" [value]="language">
            {{language.viewValue}}
        </mat-option>
    </mat-select>
</mat-form-field>

Working_Demo

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