ArticleZip > Angular2 Expression Has Changed After It Was Checked Binding To Div Width With Resize Events

Angular2 Expression Has Changed After It Was Checked Binding To Div Width With Resize Events

Have you ever encountered a situation where your Angular app's expression changes unexpectedly after being checked, especially when binding to a div's width and handling resize events? Well, fret not, as this article aims to dive into this common issue and provide you with a clear solution on how to handle this like a pro.

When dealing with changes in Angular expression at unfortunate times, specifically in scenarios involving resizing events and element bindings, it’s essential to understand the root cause of the problem. One common reason for this issue is the timing of events and change detection in Angular.

Angular's change detection mechanism can sometimes lead to unexpected expression changes, especially when dealing with elements that rely on dynamic values like the width of a div element. This can result in the expression being checked at a point where the DOM has not fully adjusted to the new width due to a resize event, leading to discrepancies in your application's behavior.

To tackle this issue effectively, one approach is to ensure that the expression binding to the div's width is updated only after the DOM has fully adjusted to the new size. A simple yet effective solution is to leverage Angular's ViewChild decorator along with Angular's Renderer2 to handle the resizing events and ensure proper updating of the expression.

Firstly, you can use the ViewChild decorator to get a reference to the div element in your component. This allows you to directly access and manipulate the properties of the div element within your component code.

Next, by utilizing Angular's Renderer2, you can safely make changes to the element properties in a way that aligns with Angular's change detection mechanism, ensuring that the expression is updated correctly after the resize event has been fully processed by the DOM.

Here's a quick example demonstrating how you can implement this solution in your Angular component:

Typescript

import { Component, ElementRef, ViewChild, AfterViewInit, Renderer2 } from '@angular/core';

@Component({
  selector: 'app-your-component',
  template: `<div></div>`
})
export class YourComponent implements AfterViewInit {
  @ViewChild('resizableDiv') resizableDiv: ElementRef;

  constructor(private renderer: Renderer2) {}

  ngAfterViewInit() {
    window.addEventListener('resize', () =&gt; {
      this.renderer.setStyle(this.resizableDiv.nativeElement, 'width', `${this.resizableDiv.nativeElement.offsetWidth}px`);
    });
  }
}

By following this approach, you ensure that the expression binding to the div's width is updated only after the DOM has fully adjusted to the new size, effectively addressing the issue of expression changes occurring at unexpected times.

In conclusion, handling Angular expression changes after being checked when binding to a div's width with resize events requires a thoughtful approach that considers the timing of events and the intricacies of Angular's change detection mechanism. By using ViewChild and Renderer2 effectively, you can ensure that your application behaves as expected even in scenarios involving dynamic element resizing and event handling.

Now armed with this knowledge, you can confidently tackle and resolve such issues in your Angular projects, ensuring a smooth and reliable user experience.

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