Dealing with the error: "Error in checking the expression as it has been altered"

Question

Dealing with the error: "Error in checking the expression as it has been altered"

I have a dialog form where users can add new projects. I want to prevent the save buttons from being enabled until all required fields are filled in correctly. I have an isValid() function that handles this validation and it appears to be working properly. However, I am encountering an issue when checking the console:

ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous 
value: 'mat-form-field-should-float: false'. Current value: 'mat-form-field-should-float: true'.

The mat-form-field causing the problem is located here:

                <mat-form-field class="input-half-width">
                    <input matInput [formControl]="name" placeholder="Project Name" #nameInput required> 
                </mat-form-field>

The specific HTML section triggering the error seems to be related to the [disabled]=!isValid() attribute. While removing it resolves the error, maintaining the validation functionality is necessary.

            <button mat-raised-button (click)="closeDialog(saveAndContinueIsClicked);">Close</button>
            <button mat-raised-button color="primary" [disabled]="buttonIsClicked || !isValid()" (click)="saveAndCloseDialog(false); buttonIsClicked=true; saveAndContinueIsClicked=true;">Save and Continue</button>
            <button mat-raised-button color="primary" [disabled]="buttonIsClicked || !isValid()" (click)="saveAndCloseDialog(); buttonIsClicked=true;">Save and Close</button>

This is what my isValid() function looks like:

  isValid() {
    if (this.projectName.value == null || this.projectName.value == "") {
        this.error = 'Name is required';
        this.nameElement.nativeElement.focus(); // The error disappears if I remove this line.
        return false;
    }

In my component, nameElement is defined as follows:

@ViewChild('nameInput')
nameElement: any;

I understand the underlying cause of the issue. Focusing on the name field when the dialog opens causes the label to float, leading to the error. I might consider removing the focus line for the name input but would prefer to find a workaround if possible.

angular typescript exception

Answer 1

Answer №1

First Step

Begin by including the following code in the appropriate module:

import { MAT_FORM_FIELD_DEFAULT_OPTIONS } from '@angular/material/form-field';

  providers: [
  // ...,
   {
      provide: MAT_FORM_FIELD_DEFAULT_OPTIONS,
      useValue: { floatLabel: 'always' },
    },
  // ...
  ],

Second Step

Then, in the relevant component, make sure to add the given snippet:

export class MyComponentWithConsoleError implements OnInit, AfterContentChecked {
  ngOnInit(): void {
    // ...
    this.cd.detach();
  }
  
   ngAfterContentChecked(): void {
    this.cd.detectChanges();
  }
  
}

Answer 2

First Step

Begin by including the following code in the appropriate module:

import { MAT_FORM_FIELD_DEFAULT_OPTIONS } from '@angular/material/form-field';

  providers: [
  // ...,
   {
      provide: MAT_FORM_FIELD_DEFAULT_OPTIONS,
      useValue: { floatLabel: 'always' },
    },
  // ...
  ],

Second Step

Then, in the relevant component, make sure to add the given snippet:

export class MyComponentWithConsoleError implements OnInit, AfterContentChecked {
  ngOnInit(): void {
    // ...
    this.cd.detach();
  }
  
   ngAfterContentChecked(): void {
    this.cd.detectChanges();
  }
  
}

Answer 3

Answer №2

After implementing change detection, everything ran smoothly without the need for including the MAT_FORM_FIELD_DEFAULT_OPTIONS provider

Answer 4

After implementing change detection, everything ran smoothly without the need for including the MAT_FORM_FIELD_DEFAULT_OPTIONS provider

Answer 5

Answer №3

The solution that worked for me was including the following code snippet:

  ngAfterContentChecked(): void {
    this.cdr.detectChanges();
  }

I added this to my dialog component in hopes that it may help someone else facing a similar issue.

Don't overlook the necessity of adding ChangeDetectorRef to the constructor as well.

  constructor(
    private readonly dialogRef: MatDialogRef<MyRandomModalComponent>,
    private cdr: ChangeDetectorRef, # <--- this line.
  ) {}

Answer 6

The solution that worked for me was including the following code snippet:

  ngAfterContentChecked(): void {
    this.cdr.detectChanges();
  }

I added this to my dialog component in hopes that it may help someone else facing a similar issue.

Don't overlook the necessity of adding ChangeDetectorRef to the constructor as well.

  constructor(
    private readonly dialogRef: MatDialogRef<MyRandomModalComponent>,
    private cdr: ChangeDetectorRef, # <--- this line.
  ) {}

Answer 7

Answer №4

To resolve the issue, consider encapsulating the problematic code block within a setTimeout function. This approach can help in handling the "error" effectively:

isValid() {
    if (this.projectName.value == null || this.projectName.value == "") {
        setTimeout(() => {
            this.error = 'Name is required';
            this.nameElement.nativeElement.focus();
            return false;
        });
    }
}

Answer 8

To resolve the issue, consider encapsulating the problematic code block within a setTimeout function. This approach can help in handling the "error" effectively:

isValid() {
    if (this.projectName.value == null || this.projectName.value == "") {
        setTimeout(() => {
            this.error = 'Name is required';
            this.nameElement.nativeElement.focus();
            return false;
        });
    }
}

Dealing with the error: "Error in checking the expression as it has been altered"

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

What is the best way to prevent re-initialization of a child component when there are changes in the

Error: Name 'AudioDecoder' could not be located

Why is the bearing attribute important in determining the location of an object?

Angular 4 project occupying significant disk space

Property ngIf in Angular is not being supplied by any relevant directive within the embedded template

Can a form be submitted using ViewChild in Angular5?

Angular4 + Universal + ng-bootstrap triggering an 'Unexpected token import' error

Learn how to implement Angular 8 to listen for changes in an observable within an interceptor

Upon upgrading @types/angular, I encountered error TS2694 stating that the namespace 'angular' does not have an exported member 'xxx'

What is the appropriate interface for determining NavLink isActive status?

I am experiencing difficulties with my Angular 8 NPM package as it is unable to locate its own

Creating a delayed queue using RxJS Observables can provide a powerful and

The proper method for retrieving FormData using SyntheticEvent

Testing the Observable StatusChanges in Angular Forms: A Step-by-Step Guide

What steps should I follow to have my edit form component extract values from HTML in Angular?

Troubleshooting issue with Angular2 Dart ngFor not refreshing view with WebSockets data stream

Tips for displaying a notification about data filtering and loading using the Async Pipe in Angular

What is the most effective way to handle DOM events in Angular 8?

Refresh the context whenever the state object changes

Generating an interactive table using JSON with Angular 5