Angular 15 experiences trouble with child components sending strings to parent components

I am facing a challenge with my child component (filters.component.ts) as I attempt to emit a string to the parent component. Previously, I successfully achieved this with another component, but Angular seems to be hesitant when implementing an *ngFor loop through a string array to pass the category string to the method. Despite adding a console log to the onShowCategory() method in home.component.ts, no string values seem to get logged, indicating that the values are not being passed to the parent upon activation of the click event. Here is the modified code snippet (the arrows inserted for clarity purposes point to the lines of relevance):

filters.component.html:

<mat-expansion-panel *ngIf="categories">
    <mat-expansion-panel-header>
        <mat-panel-title>CATEGORIES</mat-panel-title>
    </mat-expansion-panel-header>
    <mat-selection-list [multiple]="false">
        <mat-list-option *ngFor="let category of categories" [value]="category"> <--------
            <button (click)="onShowCategory(category)">{{ category }}</button> <--------
        </mat-list-option>
    </mat-selection-list>
</mat-expansion-panel>

filters.component.ts:

@Component({
  selector: 'app-filters',
  templateUrl: './filters.component.html',
  styleUrls: []
})
export class FiltersComponent {
  @Output() showCategory = new EventEmitter<string>() <-------

  categories: string[] = ['shoes', 'sports']; <-------

  onShowCategory(category: string): void { <-------
    this.showCategory.emit(category); <-------
  }
}

home.component.html:

<mat-drawer-container [autosize]="true" class="min-h-full max-w-7xl mx-auto border-x">
    <mat-drawer mode="side" class="p-6" opened>
        <app-filters (showCategory)="onShowCategory($event)"></app-filters> <-------
    </mat-drawer>
    
    <mat-drawer-content class="p-6">
        <app-products-header (columnsCountChange)="onColumnsCountChange($event)"></app-products-header>
        
        {{ category }} <----- should display the category when selected
    </mat-drawer-content>
</mat-drawer-container>

home.component.ts:

import { Component } from '@angular/core';

@Component({
  selector: 'app-home',
  templateUrl: './home.component.html',
  styleUrls: []
})
export class HomeComponent {
  cols = 3;
  category: string | undefined; <-------
  
  onColumnsCountChange(colsNumber: number): void {
    this.cols = colsNumber
  }
 
  onShowCategory(newCategory: string): void { <-------
    this.category = newCategory; <-------
  }
}

I have meticulously reviewed and traced the variables multiple times but continue to struggle. When passing the category from the child component template to the onShowCategory method and emitting it to the parent, I call the EventEmitter from the parent component using the $event variable which ideally should update the value of the category property in the home component. Spelling has been double-checked and tag positions adjusted, yet a console.log added to the method does not produce any output in the console, and the string fails to appear on the home template. What mistake might I be making?

Answer №1

Make sure your parent HTML includes a messageEvent. Test it out to see if it functions properly.

<app-category-list (messageEvent)="onCategorySelected($event)"></app-category-list>

<app-header (messageEvent)="onHeaderChange($event)"></app-header>

It's helpful to add console.log statements when configuring EventEmitters, so you can track down any potential issues.

Answer №2

After stepping away for a bit and scouring the web for solutions (but coming up empty-handed), I decided to take a different approach that ultimately led me to crack the problem.

I made the following adjustment:

<mat-list-option *ngFor="let category of categories" [value]="category">
            <button type="button" (click)="onShowCategory(category)">{{ category }}</button>
        </mat-list-option>

To

<mat-list-option *ngFor="let category of categories" (click)="onShowCategory(category)" [value]="category">
      <div>{{ category }}</div>
</mat-list-option>

Surprisingly, changing the location of the click event from the button to its parent tag resolved the issue. It's still unclear why the click event must be placed on the parent element rather than the button itself. My reasoning behind this amendment was that the click event didn't seem to trigger or the data in the categories array weren't being passed correctly to the method. Hopefully, this solution proves beneficial to someone facing a similar challenge in the future.

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