Angular 4 How To Watch An Object For Changes

Watching an object for changes in Angular 4 can be a powerful tool to keep your application's data up to date and respond dynamically to any modifications. In this guide, we will walk you through the steps on how to implement this feature effectively in your project.

One of the key features that make Angular stand out is its ability to watch for changes in data. In our scenario, we want to monitor an object for any modifications and trigger actions based on those changes.

To start with, we need to leverage Angular's ChangeDetectorRef to detect and respond to changes in our object. First, inject ChangeDetectorRef in the component where you want to watch the object:

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

constructor(private cdr: ChangeDetectorRef) {}

Once we have access to ChangeDetectorRef, we can create a method to watch the object for changes. Let's say we have an object named 'myObject':

myObject = { name: 'John Doe' };

watchObjectForChanges() {
  this.myObject = { name: 'Jane Doe' };
  this.cdr.detectChanges();
}

In the above code snippet, we updated the 'myObject' property with a new value and then called 'detectChanges()' on the ChangeDetectorRef instance. This will trigger Angular's change detection mechanism and update the view accordingly.

It's important to note that Angular's change detection is smart and efficient, so it won't trigger unnecessary updates if the values remain the same after the change.

Another approach to watch an object for changes is by leveraging RxJS observables. You can create a BehaviorSubject to track changes in your object:

import { BehaviorSubject } from 'rxjs';

myObject$ = new BehaviorSubject({ name: 'John Doe' });

watchObjectForChanges() {
  this.myObject$.next({ name: 'Jane Doe' });
}

By using BehaviorSubject and its next() method, you can emit new values to the observable stream, and any subscribers will automatically be notified of these changes.

Remember, when you subscribe to the observable in your template or component, Angular will handle the updates for you behind the scenes.

Watching an object for changes in Angular 4 is a valuable technique that allows you to create responsive and dynamic applications. By implementing the methods mentioned above, you can efficiently monitor your objects and trigger actions based on any modifications.

Keep in mind that Angular's change detection mechanism is optimized for performance, so make sure to use it wisely and avoid unnecessary updates to improve the efficiency of your application.