Ember.js Route addObserver() Method

Ember.js is an open-source JavaScript framework used for developing large client-side web applications which is based on Model-View-Controller (MVC) architecture. Ember.js is one of the most widely used front-end application frameworks. It is made to speed up development and increase productivity. Currently, it is utilized by a large number of websites, including Square, Discourse, Groupon, Linked In, Live Nation, Twitch, and Chipotle.

The addObserver() method is used to register the observer to the property.

Syntax:

addObserver( key, target, method, sync );

Parameters:

• key: It is the key that will be observed.
• target: It is the object for which the observer will invoke. 
• method: It is the method name that will invoke when the observer gets something. 
• sync: It defines whether to sync the observer or not. 

Return: Observable. 

Steps to Install and Run Ember.js:

Step 1: To run the following examples you will need to have an ember project with you. To create one, you will need to install ember-cli first. Write the below code in the terminal:

npm install ember-cli

Step 2: Now you can create the project by typing in the following piece of code:

ember new <project-name> --lang en

To start the server, type:

ember serve

Example 1: Type the following code to generate the route for this example:

ember generate route addObserver1

app/components/arr.js

Javascript

import Component from '@glimmer/component';
import Ember from 'ember';
import { tracked } from '@glimmer/tracking';
import { action, addObjects, set, get } from '@ember/object';
export default Ember.Component.extend({
    value: 'Oxygen',
    init() {
        this._super(...arguments);
        this.addObserver('value', this, 'change');
        alert('Route Init() is initiated');
    },
    change() {
        console.log('Value changed ')
    },
    p1: [
        'Oxygen',
        'Source Code',
        'Infinite',
        'Tenet',
        'SpiderHead',
        'The Thing',
        'A Quiet Place',
        'The Invisible Man',
        'Looper',
        'Ad Astra',
    ],


  @action
remove(data) {
    this.p1.set('[]', this.p1.without(data));
},
@action
print(){
    let ans = this.p1.get('[]');
    alert(ans.join('\n'))
}

})

app/components/arr.hbs

HTML

<ul>
    <h3>{{yield}} </h3>
      {{#each this.p1 as |party|}}
           <li>{{party}}</li>
       {{/each}}
</ul>
<br />
{{input value=this.value}}
<br />
<input
    type="button"
      id="check-atIndex"
      value="Remove"
      {{action "remove" this.value}}
/>
<br /><br />
<input
    type="button"
      id="print-item"
      value="Print All Items"
      {{action "print"}}
/>

• app/templates/addObserver.hbs

HTML

<Arr> <h3>List is : </h3></Arr>

Output:

Ember.js Route addObserver() Method

Example 2: Type the following code to generate the route for this example:

ember generate route addObserver2

app/components/arr2.js

Javascript

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { action } from '@ember/object';
import { mapBy } from '@ember/object';
import Ember from 'ember';
let Student = Ember.Object.extend({
    // these will be supplied by `create`
    firstName: null,
    lastName: null,
    fullName: Ember.computed('firstName', 'lastName', function () {
        return `${this.firstName} ${this.lastName}`;
    }),

    Changed: Ember.observer('fullName', function () {
        console.log(`fullName changed to: ${this.fullName}`);
    }),
});

export default Ember.Component.extend({
    students: [
        Student.create({
            firstName: 'Kasual',
            lastName: 'Singh',
            Id: 'stu2',
        }),
        Student.create({
            firstName: 'Yehuda',
            lastName: 'Katz',
            Id: 'stu0',
        }),
        Student.create({
            firstName: 'Yella',
            lastName: 'melo',
            Id: 'stu1',
        }),
        Student.create({
            firstName: 'Pokhu',
            lastName: 'Verma',
            Id: 'stu3',
        })],
  @tracked
value: 'Pokhu',

  @tracked
value2: 'Pokhraj',

  @action
print(data1, data2) {
    let ans = this.students.find((item) =>
        item.get('firstName') == data1)
    ans.set('lastName', data2)
}
})

app/components/arr2.hbs

HTML

{{yield}}
<table>
    <tr>
        <th>Name</th>
        <th>Id</th>
      </tr>
      {{#each this.students as |detail|}}
    <tr>
        <td>{{detail.fullName}}</td>
          <td>{{get detail "Id"}}</td>
    </tr>
      {{/each}}
</table>
<br />
{{input value=this.value}}
{{input value=this.value2}}
<br />
<input
    type="button"
      id="set-code"
      value="Update Student details"
      {{action "print" this.value this.value2}}
/>

app/templates/addObserver2.hbs

HTML

<Arr2><h3>Students Details :</h3></Arr2>

Output:

Ember.js Route addObserver() Method

Reference: https://api.emberjs.com/ember/4.6/classes/Route/methods/addObserver?anchor=addObserver