Using Events in Ionic to Pass Data & Messages Between Pages

The first step in getting the event system to work is to import and inject the Events service into both the sending and the receiving pages:

import { Component, Events } from 'ionic-angular';

import { Component, Events } from 'ionic-angular';

Now that we have imported and injected the Events service into both pages we can start publishing and subscribing to events using the service’s publish and subscribe methods.

On Page1, we’ll publish a message when a button is pressed:

handleClick(){
  this.events1.publish('my-message', '👋 Hello from page1!');
}

Then on page 2 we’ll subscribe to receive messages published using the my-message key (called a topic in Ionic):

constructor(public events2: Events){
  this.events2.subscribe('my-message', (data) =>{
    console.log(data); // 👋 Hello from page1!
  });
}

As soon as the event is published and page2 is initialized, the subscribe event will be triggered and execute the code with the data being passed.

There are many practical applications to use the event system. For example, I’ve used it to pop back to a page using the navController while also updating some information on the page that gets popped into.

Normally, when navigating to a page using navController’s push method, we can pass data as navParams, but the pop method doesn’t have such capability, so the event pub-sub service comes-in really handy.

Take a look at this mini application for instance:

import { Component, Events } from 'ionic-angular';
import { NavController } from 'ionic-angular';

@Component({
  selector: 'page-game',
  templateUrl: 'game.html'
})
export class GamePage {
  constructor(
    public events: Events,
    public navController: NavController
  ) {
    this.events.subscribe('stats', statsData => {
      console.log(statsData);
    });
  }

import { Component, Events } from 'ionic-angular';
import { NavController } from 'ionic-angular';

@Component({
  selector: 'page-show-winner',
  templateUrl: 'show-winner.html'
})
export class ShowWinnerPage {
  constructor(
    public events: Events,
    public navController: NavController
  ) {}

The events service in the GamePage class will continue to be subscribed to receive messages for the life of the application unless it is unsubscribed using something like this:

private unsubscribeToEvents() {
  this.events.unsubscribe('stats', () => {
    console.log('Unsubscribed!');
  });
}