Angular is not programmed to automatically reflect updates made to my string array

Question

Angular is not programmed to automatically reflect updates made to my string array

let signalRServerEndPoint = 'https://localhost:44338';
this.connection = $.hubConnection(signalRServerEndPoint);
this.proxy = this.connection.createHubProxy('MessagesHub');

this.proxy.on("ReceiveMessage", (message) => {
  console.log(message); //LOG IS OKAY
  this.listMessages.push(message); // PUSH IS OKAY
  console.log(this.listMessages); // LOG IS OKAY IS OKAY
});

The listmessages array contains strings. The console.log() functions are working correctly and the this.listMessages.push(message) is functioning properly as well, as the second console.log displays the updated string array. However, an issue arises in the UI where the new entries in listMessages do not automatically populate. Only when something is typed in the textbox or the send button is clicked again, does the latest entry appear. Seeking assistance in resolving this problem.

<div *ngFor="let listMessage of listMessages;let indexs = index;">
    <div class="row align-items-center" style="margin-bottom: 5px;" *ngIf="indexs % 2 == 0">
        <div class="col-lg-7">
            <div class="row">
                <img [src]="createImagePath('userphoto/202431775reyes.jpg')" class="avatar avatar-sm rounded-circle" style="margin-left: 20px; max-width: 70px; max-height: 50px;" />
                <div class="card-header bg-gradient-success" style="margin-left: 20px; border-radius: 25px; background-color: #f1f0f0;">
                    <h4 style="margin-bottom: -10px; margin-top: -10px;" class="text-white">{{listMessage}}</h4>
                </div>
            </div>
            <h6 class="text-primary" style="margin-left: 10px;">Anthony Earl Cuartero: 12:00 PM | Aug 13</h6>
        </div>
    </div>
</div>

javascript angular typescript signalr

Answer 1

Answer №1

It appears that the issue lies in the change detection not being triggered due to the variable reference not being modified. To resolve this, you can use the destructuring operator instead of the push method. Replace the push statement with

this.listMessages = [...this.listMessages, message];

Alternatively, you can keep the push statement and manually trigger change detection using Angular's ChangeDetectorRef.

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

export class AppComponent {
  constructor(private changeDetectorRef: ChangeDetectorRef) { }

this.proxy.on("ReceiveMessage", (message) => {
  this.listMessages.push(message);
  this.changeDetectorRef.detectChanges();
});

Answer 2

It appears that the issue lies in the change detection not being triggered due to the variable reference not being modified. To resolve this, you can use the destructuring operator instead of the push method. Replace the push statement with

this.listMessages = [...this.listMessages, message];

Alternatively, you can keep the push statement and manually trigger change detection using Angular's ChangeDetectorRef.

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

export class AppComponent {
  constructor(private changeDetectorRef: ChangeDetectorRef) { }

this.proxy.on("ReceiveMessage", (message) => {
  this.listMessages.push(message);
  this.changeDetectorRef.detectChanges();
});

Answer 3

Answer №2

It seems that there is a challenge with integrating jQuery and Angular, causing the events to not trigger change detection properly. It would be ideal to find alternatives to using jQuery, such as utilizing SignalR without it or exploring better-integrated SignalR/Angular libraries available.

In the meantime, though untested, you can potentially make it work by leveraging NgZone to incorporate it into Angular's change detection mechanism. Here's a possible approach:

constructor(private ngZone: NgZone) {}

this.proxy.on("ReceiveMessage", (message) => {
  this.ngZone.run(() => {
    console.log(message); // Log is successful
    this.listMessages.push(message); // Push works fine
    console.log(this.listMessages); // Log output is okay
  });
});

It might be beneficial to create a websocket wrapper service to handle all websocket events, thereby eliminating the need to use NgZone extensively in your websocket usage.

Answer 4

It seems that there is a challenge with integrating jQuery and Angular, causing the events to not trigger change detection properly. It would be ideal to find alternatives to using jQuery, such as utilizing SignalR without it or exploring better-integrated SignalR/Angular libraries available.

In the meantime, though untested, you can potentially make it work by leveraging NgZone to incorporate it into Angular's change detection mechanism. Here's a possible approach:

constructor(private ngZone: NgZone) {}

this.proxy.on("ReceiveMessage", (message) => {
  this.ngZone.run(() => {
    console.log(message); // Log is successful
    this.listMessages.push(message); // Push works fine
    console.log(this.listMessages); // Log output is okay
  });
});

It might be beneficial to create a websocket wrapper service to handle all websocket events, thereby eliminating the need to use NgZone extensively in your websocket usage.

Answer 5

Answer №3

When updating an array with push, the reference remains the same, causing the UI not to update. To solve this issue, you can create a new array using either the filter method or the spread operator. Essentially, you need to generate a fresh array by combining the original array with the updated data. It's important to note that in JavaScript, arrays are considered reference types.

Answer 6

When updating an array with push, the reference remains the same, causing the UI not to update. To solve this issue, you can create a new array using either the filter method or the spread operator. Essentially, you need to generate a fresh array by combining the original array with the updated data. It's important to note that in JavaScript, arrays are considered reference types.

Angular is not programmed to automatically reflect updates made to my string array

Answer №1

Answer №2

Answer №3

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