Tips for accessing and adjusting an ngModel that is populated by an attribute assigned via ngFor

Looking for guidance on how to modify an input with ngModel attribute derived from ngFor, and update its value in the component. Here is my code snippet for reference:

HTML

FRONT

The goal here is to adjust [(ngModel)] = "item.days" based on button clicks, but I'm unsure how to access it within a component function for dynamic changes.

My attempt at validating that the input should not go below 0 failed, so I decided to hide the input field instead. Would appreciate any assistance on this matter. Thank you.

javascriptangulartypescriptangular2-ngmodel

Answer №1

To determine which value to change, you must pass the index to your change value function. Modifying the array value will prompt Angular's change detection to update the ngModel in the HTML.

changeValue(value, index): void {
    this.complexities[index].days += value;

    if (this.complexities[index].days < 0) {
      this.complexities[index].days = 0;
    }
  }

Your button implementation may appear as follows:

<button
  type="button"
  class="btn btn-default btn-xs rounded"
  (click)="changeValue(-1, i)">

For incrementing by +1, simply pass that value instead. To validate input, consider adding the following line within the <input> tag:

(change)="changeValue(0, i)"

This will keep the number of days unchanged but reset the value to 0 if a negative input is provided.

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