The situation I find myself in frequently is that the Angular component Input

Question

The situation I find myself in frequently is that the Angular component Input

There seems to be an issue with a specific part of my application where the inputs are not binding correctly.

The component in question is:

@Component({
    selector : 'default-actions',
    templateUrl : './default.actions.template.html',
    styleUrls: [ './default.actions.style.scss' ],
    encapsulation: ViewEncapsulation.None,
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class DefaultActionsComponent
{
    protected entityId;
    protected uuid = UUID.UUID();
    protected extraForms;

    @Input() protected data;
    @Input() protected structure;
    @Input() protected targetId;
    @Input() protected table;
    @Input() protected row;
    @Input() protected modal: ModalDirective;
    @Input() protected entity;
    @Input() protected entityObject: Entity;
    @Input() protected parentWrapper;
    @Input() protected foo;

    constructor(
        protected translate: TranslateService,
        protected activatedRoute: ActivatedRoute,
        protected actionService: DefaultActionsService,
        protected router: Router,
        protected entityService: EntityService,
        protected http: HttpAuthenticationService
    ) {}

    public ngOnInit() {
        console.log(this.foo);
    }

The component is being used here:

<default-actions
    [table]="table['defaultListingTableComponent']"
    [row]="row"
    [foo]="'bar'"
    [modal]="modal"
    [structure]="availableColumns"
    [entityObject]="entityObject"
    [targetId]="selectedRows()">
</default-actions>

I added the foo input for debugging purposes. However, when I check the console using console.log(this.foo);, it returns undefined. The same issue persists with other inputs as well.

Although all other components in my application are functioning properly, there seems to be some trouble with this particular component that I'm having difficulty identifying.

angular typescript

Answer 1

Answer №1

Have you considered utilizing the OnInit interface to ensure functionality? It might be worth a try.

Answer 2

Have you considered utilizing the OnInit interface to ensure functionality? It might be worth a try.

Answer 3

Answer №2

UPDATE:

Here's a Stackblitz sample I created: https://stackblitz.com/edit/angular-qrgy7k

Helpful Tip:

Instead of directly passing a string like [foo] = "'bar'", consider creating a variable in the parent component and then pass it as [foo] = "yourVariable"

Parent Component HTML:

<hello name="{{ name }}"></hello>
<p>
  Start editing to see some magic happen :)
</p>
<app-demo
[mydata]="datatopass"
>  
</app-demo>

Parent Component TS:

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

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  name = 'Angular';
  datatopass = "sad";
}

Child Component HTML:

<p>
demo works!
</p>
<div>
  Data: {{ mydata }}
</div>

Child component TS:

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

@Component({
  selector: 'app-demo',
  templateUrl: './demo.component.html',
  styleUrls: ['./demo.component.css']
})
export class DemoComponent implements OnInit {

  @Input() mydata;

  constructor() { }

  ngOnInit() {
    console.log(this.mydata);
  }

}

ngOnInit() will run when the component is initialized, but at that point, the properties you've bound may not yet contain data from the parent component. You can try using ngOnChanges() or ngAfterViewInit().

One approach is to use Observables and Subjects.

Answer 4

UPDATE:

Here's a Stackblitz sample I created: https://stackblitz.com/edit/angular-qrgy7k

Helpful Tip:

Instead of directly passing a string like [foo] = "'bar'", consider creating a variable in the parent component and then pass it as [foo] = "yourVariable"

Parent Component HTML:

<hello name="{{ name }}"></hello>
<p>
  Start editing to see some magic happen :)
</p>
<app-demo
[mydata]="datatopass"
>  
</app-demo>

Parent Component TS:

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

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent  {
  name = 'Angular';
  datatopass = "sad";
}

Child Component HTML:

<p>
demo works!
</p>
<div>
  Data: {{ mydata }}
</div>

Child component TS:

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

@Component({
  selector: 'app-demo',
  templateUrl: './demo.component.html',
  styleUrls: ['./demo.component.css']
})
export class DemoComponent implements OnInit {

  @Input() mydata;

  constructor() { }

  ngOnInit() {
    console.log(this.mydata);
  }

}

ngOnInit() will run when the component is initialized, but at that point, the properties you've bound may not yet contain data from the parent component. You can try using ngOnChanges() or ngAfterViewInit().

One approach is to use Observables and Subjects.

Answer 5

Answer №3

As stated by @Yash, the ngOnInit function is the appropriate place to handle that. However, you could also include the ngOnChanges method and add a console.log within it. Initially, the value may be undefined, but as soon as there are changes in the input, it will trigger and you may retrieve the updated value at that point.


ngOnChanges() {
  console.log(this.bar)
}

Answer 6

As stated by @Yash, the ngOnInit function is the appropriate place to handle that. However, you could also include the ngOnChanges method and add a console.log within it. Initially, the value may be undefined, but as soon as there are changes in the input, it will trigger and you may retrieve the updated value at that point.


ngOnChanges() {
  console.log(this.bar)
}

Answer 7

Answer №4

Have you ever experimented with using Observables instead? It seems like there might be an issue with your input still being undefined when it is sent to the child component. @Input can sometimes behave strangely if you're not familiar with its functionality.

Answer 8

Have you ever experimented with using Observables instead? It seems like there might be an issue with your input still being undefined when it is sent to the child component. @Input can sometimes behave strangely if you're not familiar with its functionality.

Answer 9

Answer №5

If you want to test out the implementation of AfterViewChecked, check if the ngAfterViewChecked method contains a value like this:

@Component({
    selector : 'default-actions',
    templateUrl : './default.actions.template.html',
    styleUrls: [ './default.actions.style.scss' ],
    encapsulation: ViewEncapsulation.None,
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class DefaultActionsComponent implements AfterViewChecked {
    protected entityId;
    protected uuid = UUID.UUID();
    protected extraForms;

    @Input() protected data;
    @Input() protected structure;
    @Input() protected targetId;
    @Input() protected table;
    @Input() protected row;
    @Input() protected modal: ModalDirective;
    @Input() protected entity;
    @Input() protected entityObject: Entity;
    @Input() protected parentWrapper;
    @Input() protected foo;

    constructor(
        protected translate: TranslateService,
        protected activatedRoute: ActivatedRoute,
        protected actionService: DefaultActionsService,
        protected router: Router,
        protected entityService: EntityService,
        protected http: HttpAuthenticationService
    ) {}

    public ngOnInit() {
        console.log(this.foo);
    }

    ngAfterViewChecked() {
      console.log(this.foo);
    }

Answer 10

If you want to test out the implementation of AfterViewChecked, check if the ngAfterViewChecked method contains a value like this:

@Component({
    selector : 'default-actions',
    templateUrl : './default.actions.template.html',
    styleUrls: [ './default.actions.style.scss' ],
    encapsulation: ViewEncapsulation.None,
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class DefaultActionsComponent implements AfterViewChecked {
    protected entityId;
    protected uuid = UUID.UUID();
    protected extraForms;

    @Input() protected data;
    @Input() protected structure;
    @Input() protected targetId;
    @Input() protected table;
    @Input() protected row;
    @Input() protected modal: ModalDirective;
    @Input() protected entity;
    @Input() protected entityObject: Entity;
    @Input() protected parentWrapper;
    @Input() protected foo;

    constructor(
        protected translate: TranslateService,
        protected activatedRoute: ActivatedRoute,
        protected actionService: DefaultActionsService,
        protected router: Router,
        protected entityService: EntityService,
        protected http: HttpAuthenticationService
    ) {}

    public ngOnInit() {
        console.log(this.foo);
    }

    ngAfterViewChecked() {
      console.log(this.foo);
    }

Answer 11

Answer №6

The issue arises from the usage of ChangeDetectionStrategy.onPush.

When using OnPush, the change detection mechanism operates by comparing the references of the component's inputs. Since the object reference remains constant in your scenario, the OnPush change detector does not detect any changes.

To delve deeper into this topic, you may find more detailed explanations at the following link:

Answer 12

The issue arises from the usage of ChangeDetectionStrategy.onPush.

When using OnPush, the change detection mechanism operates by comparing the references of the component's inputs. Since the object reference remains constant in your scenario, the OnPush change detector does not detect any changes.

To delve deeper into this topic, you may find more detailed explanations at the following link:

The situation I find myself in frequently is that the Angular component Input

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Similar questions

Is it possible to bind an http post response to a dropdown list in Angular?

Tips on implementing conditional validators in Angular's formBuilder

What do you do when schema.parseAsync cannot be found?

Upon receiving the API response, my Angular webpage is failing to redirect to a different page

Merge topics together in RxJS like zip

How to ensure that Excel recognizes dates as actual dates in a column automatically when using xlsx in Angular

What are the steps for integrating Angularfire2 into an Angular application?

Comparing the cost of memory and performance between using classes and interfaces

What is the best way to implement a switch case for the value of a property within an object in a TypeScript file?

Performing a search through a string array and updating a specific portion of each string

"Connecting multiple URLs to the same router link: A step-by-step guide

Avoid including any null or undefined values within a JSON object in order to successfully utilize the Object.keys function

Exploring VSCode Debugger with Typescript: Traversing through Step Over/Into leads to JavaScript file路径

Troubleshooting Next.js 14.1 Pre-rendering Issue: A Step-by-Step Guide

Angular `CORS` Ailment

Exceed the capacity of a React component

Using Typescript and React to assign an array object to state

The mat-table's data source is failing to refresh and display the latest

Error message: In the combination of NextJs and Redux, an issue has occurred where the program is unable to access properties of null, specifically in

Implement FieldResolver in TypeGraphQL for an array of objects