IONIC2/Angular2 ngOnChange doesn't work

Question

I'm new to Angular2 and I've been struggling for a while with this problem and have found no solution to it online.

[on ionic2!]

I want to use ngOnChanges() so i can detect changes to zonaid:

estados.html:

<ion-item>
       <ion-label color="branco">Zonas</ion-label>


              <ion-select *ngIf="isTrue2" [(ngModel)]=zonaid>
                 <ion-option value={{bicho.zonas}} *ngFor="let bicho of idespecie">
                    {{bicho.zonas}}
                 </ion-option>
             </ion-select>


              <ion-select *ngIf="!isTrue2" [(ngModel)]="zonaid">
                 <ion-option value={{item.id}} *ngFor="let item of itemsZon" >
                    {{item.codigo}}
                 </ion-option>

              </ion-select>
     </ion-item>

idespecie and itemsZon are parts of .json files

estados.ts

import { Component, Input, SimpleChanges, OnChanges } from '@angular/core';
import { NavController } from 'ionic-angular';
import { IpmaBivService} from '../../app/services/ipmabiv.service'
import { Http } from '@angular/http';

@Component({
  selector: 'page-estados',
  templateUrl: 'estados.html'
})
export class EstadosPage {
   itemsZon: any;
   itemsEsp: any;
   zonaEscolhida: any;

   @Input()
   zonaid: string;


   idzona: '';
   idespecie: any[];

   isTrue1:boolean = false;
   isTrue2:boolean = false;
   constructor(public navCtrl: NavController, private ipmaBivService:IpmaBivService) {
  }
  ngOnChanges(changes: SimpleChanges){
     console.log('ngOnChanges ran');
     if(this.zonaid != ''){
        this.isTrue1 = true;
        this.getJsonZonas(this.zonaid);
     }
     if(this.especie != ''){
        this.isTrue2 = true;
        this.getJsonEspecies(this.especie);
     }
 }

}
  ngOnInit(){
     this.getDataZonas('zonas')
     this.getDataEspecies('especies')
   //   this.getData('especies')
 }
 }

app.module.ts

    import { BrowserModule } from '@angular/platform-browser';
import { ErrorHandler, NgModule } from '@angular/core';
import { IonicApp, IonicErrorHandler, IonicModule } from 'ionic-angular';
import { HttpModule, JsonpModule } from '@angular/http';

import { MyApp } from './app.component';
import { HomePage } from '../pages/home/home';
import { ListPage } from '../pages/list/list';
import { EstadosPage } from '../pages/estados/estados';
import { OutrosPage } from '../pages/estados/outros';

import { StatusBar } from '@ionic-native/status-bar';
import { SplashScreen } from '@ionic-native/splash-screen';

@NgModule({
  declarations: [
    MyApp,
    HomePage,
    ListPage,
    EstadosPage,
    OutrosPage
  ],
  imports: [
    BrowserModule,
    IonicModule.forRoot(MyApp),
    HttpModule,
    JsonpModule
  ],
  bootstrap: [IonicApp],
  entryComponents: [
    MyApp,
    HomePage,
    ListPage,
    OutrosPage,
    EstadosPage

  ],
  providers: [
    StatusBar,
    SplashScreen,
    {provide: ErrorHandler, useClass: IonicErrorHandler}
  ]
})
export class AppModule {}

Everything is happening in the same component (ionic page).

My goal is just to be able to run a method whenever zonaid changes. If you think there is a better way than goin through ngOnChanges, pls let me know

Thanks!

Answer 1

First, remember to always add qoutes, change [(ngModel)]=zonaid to [(ngModel)]="zonaid"

Anyway, as an answer try this:

Change <ion-select *ngIf="isTrue2" [(ngModel)]=zonaid>

to

<ion-select *ngIf="isTrue2" [ngModel]="zonaid" (ngModelChange)="runYourFunction($event)">

Remember to create a public runYourFunction(event) {} in your code.

With this you'll be data binding from the component to the view, and whenever the view changes, you'll run the function runYourFunction.

Hope that helps