Angular2: Parent and Child Components Communication

Question

I\'m trying to create a parent and child component where the child component is going to have a states drop down. Can someone help me understand how I can access the states

Answer 1

Using output and emit you can easily access child data in parent component. For example

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

@Component({
  selector: 'child-component',
  template: '<div>'
      +'<span>Child Component: </span>'
      +'<span>{{name}}</span>'
      +'<button (click)="shareData()">Share data to parent</button>'
    +'</div>',
  styleUrls: ['./app.component.css']
})
export class ChildComponent {

 @Input() name: string;
 @Output() shareDataToParent = new EventEmitter();

 title : string;
 constructor(){
     this.title = 'Sharing from child to parent';
 }

 shareData(){
     this.shareDataToParent.emit(this.title);
 }
}

<child-component name="Angular" (shareDataToParent) = shareDataToParent($event)>
</child-component>

Parent component

shareDataToParent(sharedText:string){
  console.log(sharedText);
}

More info on child parent communication

Answer 2

I would define an output into your State component and triggers an event using it:

@Component({
  selector: 'state',
  providers: [FormBuilder],
  templateUrl: 'app/state.html',
  directives: []
})
export class State {
  statesDropDownValues = ['NJ', 'NY', 'PA', 'CA'];
  stateForm: ControlGroup;
  @Output()
  stateChange:EventEmitter<string> = new EventEmitter(); // <----

  constructor(fb: FormBuilder) {
    this.stateForm = fb.group({
      'state': ''
    });
  }

  setStateValue() {
    alert('State Selected: ' + this.stateForm.value.state);
    stateChange.emit(this.stateForm.value.state);
  }
}

The parent component can register on this event to be notified of changes:

<div>
  <h2>Registration Form</h2>
  <form [ngFormModel]=registrationForm (ngSubmit)="onSubmit()">
    <label>Name: </label>
    <input type="text" ngControl="name">
    <state (stateChange)="handleNewState($event)"></state>
    <button [disabled]="!registrationForm.valid">Submit</button>
  </form>
</div>

$event contains the value of the new state value.

Edit

Here is a way to save the selected state in the parent component:

export class App {
  registrationForm: ControlGroup;

  state: string;

  constructor(fb: FormBuilder) {
    this.registrationForm = fb.group({
      'name': ['', Validators.required],
      'email': ''
    });
  }

  handleNewState(state) {
    this.state = state;
  }

  onSubmit() {
    alert('Entered Name: ' + this.registrationForm.value.name);
    alert('State Selected: ' + this.state);
  }
}