What is the most effective way to retrieve the value of a child component in Angular 2 and pass it to the parent component?

I am working on a project with a child component (calendar) and a parent component (form). I need to select a value in the calendar and then access that value in the form component.

What is the best way to achieve this?

Child Component.ts:

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

@Component({
  selector: 'calendar',
  template: '
    <md2-datepicker name="mindate"
                      placeholder="Minimum Date"
                      [(ngModel)]="minDate"
                      [mode]="mode"
                      [touchUi]="touch"
                      [format]="dateFormat"
                      #minDateControl="ngModel" [fromDate]="minDateControl">
</md2-datepicker>
      <md2-datepicker name="maxdate"
                      placeholder="Maximum Date"
                      [(ngModel)]="maxDate"
                      [min]="minDate"
                      [mode]="mode"
                      [touchUi]="touch"
                      [format]="dateFormat"
                      #maxDateControl="ngModel"></md2-datepicker>
  ',
})

export class CalendarComponent implements OnInit {

  today: Date = new Date();


  minDate: Date;
  maxDate: Date;

  constructor(){

  }

  ngOnInit(){

  }
}

Parent component :

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

import { Router } from '@angular/router';

import { ChartModule,ChartComponent } from 'angular2-chartjs';
import { ChartService } from './../shared/chart.service';

import { Colors, xAxisWidth } from './../shared/data';

@Component({
  selector: 'form-js',
  template: `
    <h3 class="chartHeading">Parameter Selection Form</h3>
    <calendar></calendar>
`,
})

export class FormComponent implements OnInit {


  @Input fromDate: string;
  @Input toDate: string;

  constructor(){

  }

  ngOnInit(){

  }

  alert(fromDate);
}

How do I retrieve the from and to date values from the form component in Angular 2?

Answer №1

To establish communication between the Parent component and the Child component, utilize the @Output decorator.

For the Parent component:

@Component({
  selector: 'form-js',
  template: `
    <h3 class="chartHeading">Parameter Selection Form</h3>
    <calendar (onSelectValue)='selectValue($event)'></calendar>
  `,
})
export class FormComponent{

   selectValue( newValue : any ) {
     console.log(newValue);
   }

}

For the child component:

import {
  Component,
  OnInit,
  ViewChild,
  Input,
  Output  // Include this import
  EventEmitter // Also include this import
} from '@angular/core';

@Component({
  selector: 'calendar',
  template: '
    <md2-datepicker name="mindate"
                      placeholder="Minimum Date"
                      [(ngModel)]="minDate"
                      [mode]="mode"
                      (change)='onChange()'  // Add this event listener
                      [touchUi]="touch"
                      [format]="dateFormat"
                      #minDateControl="ngModel" [fromDate]="minDateControl"></md2-datepicker>
      <md2-datepicker name="maxdate"
                      placeholder="Maximum Date"
                      [(ngModel)]="maxDate"
                      [min]="minDate"
                      (change)='onChange()'  // Add this event listener
                      [mode]="mode"
                      [touchUi]="touch"
                      [format]="dateFormat"
                      #maxDateControl="ngModel"></md2-datepicker>
  ',
})

export class CalendarComponent implements OnInit {
  // Define this EventListener to be accessible in the parent component.
  @Output() onSelectValue = new EventEmitter<{minDate: Date , maxDate: Date}>();
  today: Date = new Date();

  minDate: Date;
  maxDate: Date;

  constructor(){

  }

  ngOnInit(){

  }

  onChange() {
     this.onSelectValue.emit( {minDate: this.minDate, maxDate:this.maxDate} );
  }

}

Answer №2

Here is another approach:

Child Component:

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

@Component({
  selector: 'calendar',
  template: `
    <md2-datepicker name="mindate"
                      placeholder="Minimum Date"
                      [(ngModel)]="minDate"
                      [mode]="mode"
                      [touchUi]="touch"
                      [format]="dateFormat"
                      #minDateControl="ngModel"></md2-datepicker>
      <md2-datepicker name="maxdate"
                      placeholder="Maximum Date"
                      [(ngModel)]="maxDate"
                      [min]="minDate"
                      [mode]="mode"
                      [touchUi]="touch"
                      [format]="dateFormat"
                      #maxDateControl="ngModel"></md2-datepicker>
  `,
})

export class CalendarComponent implements OnInit {

  minDate: Date;
  maxDate: Date;

  constructor(){

  }

  ngOnInit(){

  }

}

Parent component :

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

import { Router } from '@angular/router';

import { ChartModule,ChartComponent } from 'angular2-chartjs';
import { ChartService } from './../shared/chart.service';

import { Colors, xAxisWidth } from './../shared/data';

@Component({
  selector: 'form-js',
  template: `
    <h3 class="chartHeading">Parameter Selection Form</h3>
    <calendar #test></calendar>
    <button (click)="showAlert();"></button>
  `,
})

export class FormComponent implements OnInit {

  @ViewChild('test') calendar;

  constructor(){

  }

  ngOnInit(){

  }

  showAlert(){
    alert(this.calendar.minDate);
  }

}

I now have the ability to access ngModel properties in the showAlert() method

Answer №3

To retrieve the value of a child Component within the Parent Component, you can make use of the @ViewChild annotation.

For example:

@ViewChild('minDateControl') calendar: Md2Datepicker;

By doing this, you will have full access to all the public properties and methods of the component.

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

What is the best way to initiate multiple processes in Node.js and ensure they finish before proceeding?

When working with Node.js and TypeScript, my goal is to initiate multiple processes using the spawn function. Afterwards, I aim to ensure all of these processes are completed before proceeding to execute any additional commands. ...

Center align the mat-expansion-panel material component in a vertical orientation

When working with the mat-expansion-panel component alongside a mat-accordion, I've encountered an issue where the items are not aligning vertically at the center/middle. I'm unsure of the proper method to achieve vertical alignment for the conte ...

Cannot establish a connection with Socket.IO

I've encountered an issue with establishing a connection to Socket.IO in my node server. Although the server starts successfully with Socket.IO, I am not seeing any console logs when trying to connect to Socket. this.server.listen(this.port, () => ...

Can you explain how to incorporate a node module script into a React.js project?

I have encountered an issue where the element works perfectly fine when using an external node module, but fails to function properly when using a locally downloaded node module. Unfortunately, I am unable to identify the root cause of this problem. You c ...

Utilize Firestore for automatic saving of data from Angular Reactive Forms

In my Angular application, I am facing an issue where data entered in a form needs to be instantly saved and updated in a Firestore database. This is crucial because multiple users will be entering data simultaneously on the same form, real-time values are ...

angular5: The ngFor directive will only function properly after the second button click

Here is my current situation: 1) When the user inputs a keyword in a text field and clicks on the search icon, it triggers an HTTP request to retrieve the data. 2) The retrieved data is then rendered in HTML using ngFor. The issue I am facing is that up ...

Is there a way for me to store the current router in a state for later use

I am currently working on implementing conditional styling with 2 different headers. My goal is to save the current router page into a state. Here's my code snippet: const [page, setPage] = useState("black"); const data = { page, setPage, ...

How can a child component class in Angular 2 be initialized when extending a parent class?

Let's consider a scenario where we have a component called ChildComponent that extends from the Parent class. How do we go about initializing the ChildComponent class? In Angular 2, when this component is used in HTML, it automatically invokes the Chi ...

The edited input is not being shown on the console when using the PUT method

I retrieved the data for the input fields (title and body) from this specific source (https://jsonplaceholder.typicode.com/posts). My goal now is to modify the text in either the title or body, so that when I use console.log(), it will show the updated tit ...

Building a search feature with a customized pipe in Angular

I attempted to create my own custom pipe in Angular 6 for filtering a list of campaigns using a search box. Strangely, I am having trouble getting the filter to work on the campaign list. Below is the code snippet that I have written. This is the implemen ...

Creating and updating a TypeScript definition file for my React component library built with TypeScript

As I work on developing a React library using TypeScript, it is important to me that consumers of the library have access to a TypeScript definition file. How can I ensure that the TypeScript definition file always accurately reflects and matches the Java ...

Dealing with multiple validation error messages in Angular Material 2

Working on a form using Angular Material 2, I am implementing a template-driven approach with an email input that requires two validators: required and email. The documentation for the input component (available at https://material.angular.io/components/co ...

Troubleshooting problems with resolving deeply nested promises

My approach to utilizing promises has been effective until now. The issue arises when the console.log(this.recipe) returns undefined and console.log(JSON.stringify(recipes)) displays an empty array. This suggests that the nested promises may not be resolvi ...

Is there a way to loop through objects in Angular 2

I am working with an Array of Objects named comments, and my goal is to select only the ones that have a specific post id and copy them to another array of objects. The issue I am facing is finding a way to duplicate the object once it has been identified. ...

Could there be an issue with the way I've implemented my setInterval function?

I am currently in the process of developing a stopwatch feature using React Native and implementing the setInterval function to increase a counter and update the state accordingly: Play Function (triggered upon pressing the play button) const [isRunning ...

Troubleshooting a CORS problem with connecting an Angular application to a Node server that is accessing the Spotify

I am currently working on setting up an authentication flow using the Spotify API. In this setup, my Angular application is making calls to my Node server which is running on localhost:3000. export class SpotifyService { private apiRoot = 'http://lo ...

Unable to instantiate new object following Angular 2 installation via CLI

Trying to utilize @angular cli for a fresh angular 2 project. The installation was successful, but encountering an error when attempting to create a new site. Any solutions? /usr/local/lib/node_modules/@angular/cli/models/config/config.js:15 construct ...

Issue with PrimeNg dropdown in a modifiable data table where the chosen value is not retained

Here is the code snippet for the column in the data table: <p-column field="organization.description" header="Partner" [editable]="dtCostShare" [style]="{'width':'30%'}"> ...

Loading a Dynamic URL within a Component's template in Angular 2.0.0-rc.1

Is there a method for dynamically loading URLs in the templateUrl property? Similar to the code snippet below: @Component({ moduleId: module.id, selector: 'my-app', templateUrl: DynamicUrl, // Load DynamicUrl here styleUrls: [&ap ...

Changing the color of the pre-selected date in the mat-datepicker Angular component is a key feature that can enhance the

Is there a way to adjust the color of the preselected "today" button in mat-datepicker? https://i.stack.imgur.com/wQ7kO.png ...