Custom input and output on same name in Angular2 2 way binding

28
votes

I know how to fix my component using a different name for the output value of this component.

let me share my code

import {Component, Input, Output, EventEmitter} from '@angular/core'; import {TranslationPipe} from "../pipes/translation.pipe";

@Component({
  selector: 'msisdn-confirm',
  template: `
  <div class="msisdn-confirm">
    <div>
      <input type="text" [(ngModel)]="m1">
    </div>
    <div>
      <input type="text" [(ngModel)]="m2">
    </div>
    <p class="error">{{message}}</p>
  </div>
`
})
export class MsisdnConfirm {
  message:string;
  @Output('mobile') emitter: EventEmitter<string> = new EventEmitter<string>();
  @Input('mobile') set setMobileValue(value) {
    this.msisdn_confirm = this.msisdn = value;
  }

  set m1(value) {
    this.msisdn = value;
    if (this.valid()) {
      console.log('emit' + this.msisdn);
      this.emitter.emit(this.msisdn);
    }
  }

  set m2(value) {
    this.msisdn_confirm = value;
    if (this.valid()) {
      console.log('emit' + this.msisdn);
      this.emitter.emit(this.msisdn);
    }
  }

  get m1():string {
    return this.msisdn;
  }
  get m2():string {
    return this.msisdn_confirm
  }

  msisdn: string;
  msisdn_confirm: string;

  constructor() {

  }

  private valid(): boolean {
    if (!/06[0-9]{8}/.test(this.msisdn)) {
      this.message = new TranslationPipe().transform("Het mobiele nummer is incorrect, (bijvoorbeeld: 0612345678)")
      return false;
    } else if (this.msisdn != this.msisdn_confirm) {
      this.message = new TranslationPipe().transform("De mobiele nummers komen niet overeen")
      return false;
    }
    this.message = null;
    return true;
  }
}

So this is a very basic component which validates two strings to be a "valid" dutch Mobile number, so a confirm box so to say. Now I can get my value in the parent component by doing something like

(mobile)="myParam = $event"

What I want is to use it like 

[(mobile)]="myParam"

This only works for setting though, is this not supported on custom components?

2
data-bindingtypescriptangular

2 Answers

50
votes

For this compact syntax to work the input and output need to follow specific naming rules

[(mobile)]="myParam"

  @Output('mobileChange') emitter: EventEmitter<string> = new EventEmitter<string>();
  @Input('mobile') set setMobileValue(value) {
    this.msisdn_confirm = this.msisdn = value;
  }

Renaming inputs and outputs by passing a string parameter to the decorator is discourages. Rather use

  @Output() mobileChange: EventEmitter<string> = new EventEmitter<string>();
  @Input() set mobile(value) {
    this.msisdn_confirm = this.msisdn = value;
  }
14
votes

Another example of Gunter's code above that may help:

export class TaskBook {
  public taskBookID: number;
  public title: String; 
}

Inside component code:

   ....
    <input type="text"  pInputText [(ngModel)]="data!.title" (change)="onDataChange()" />
   ....

 @Component({
  selector: 'taskbook_edit',
  templateUrl: './taskbook_edit.component.html' 
})
    export class TaskbookEditComponent { 

      @Input() data: TaskBook;
      @Output() dataChange = new EventEmitter<TaskBook>();

      constructor() { } 

      onDataChange() { 
        this.dataChange.emit(this.data);
      }  
    }

Outside in calling component:

<taskbook_edit  [(data)]="taskbookObj" ></taskbook_edit>

 public taskbookObj: TaskBook;