Handling select event from Google Charts in Angular v2 - events

Question

I am using Angular v2 (2.0.0-beta-1) and displaying a simple chart using Google Charts.
import {Component, View} from "angular2/core";
import {Http, HTTP_PROVIDERS} from "angular2/http";
import {OnInit, OnDestroy} from 'angular2/core';
declare let io: any;
declare let google: any;
#Component({
selector:'default',
viewProviders: [HTTP_PROVIDERS]
})
#View({
templateUrl: 'app/default/default.html'
})
export class DefaultPage implements OnInit, OnDestroy {
charttitle: string;
data: any;
options: any;
timerToken: any;
chart: any;
socket: any;
constructor(http: Http) {
}
ngOnInit() {
console.log("onInit");
this.charttitle = "Sample Graph using live data";
this.options = {
title: "My Daily Activities",
is3D: true
};
this.socket = io();
this.socket.on("data_updated", (msg) => {
this.data = new google.visualization.DataTable();
this.data.addColumn('string', 'Task');
this.data.addColumn('number', 'Hours per Day');
this.data.addRows(5);
let data = JSON.parse(msg).activityData;
for (let i = 0; i < data.length; i++) {
let act = data[i];
this.data.setCell(i, 0, act.act);
this.data.setCell(i, 1, act.value);
}
this.chart.draw(this.data, this.options);
});
this.chart = new google.visualization.PieChart(document.getElementById('chart_div'));
google.visualization.events.addListener(this.chart, 'select', this.mySelectHandler);
}
mySelectHandler() {
console.trace();
console.log("Chart: " + this);
//let selectedItem = this.chart.getSelection()[0];
/*if (selectedItem) {
let value = this.data.getValue(selectedItem.row, 0);
console.log("The user selected: " + value);
}*/
}
ngOnDestroy() {
console.log("onDestroy");
this.socket.disconnect();
}
}
The problem I have is the following line.
google.visualization.events.addListener(this.chart, 'select', this.mySelectHandler);
The event is registered is when an element on the pie chart is selected the actual event handler is fired. But all the Angular JS 2 scope variables referenced by this aren't in scope. It's as if the Google Chart visualization library is running in its own scope.
I know that Angular JS has the Angular-Charts directive but we cannot use that as the company wants to use Angular v2 only.
Is there a way I can get the Google Charts API to 'bubble' an event to the event handler running on the scope of the Angular component.

Answer 1

If you want that your mySelectHandler takes part within the Angular2 context / change detection, you could leverage NgZone, as described below. This way, the changes you make in this function will update the view accordingly.
import {NgZone} from 'angular2/core';
export class DefaultPage implements OnInit, OnDestroy {
constructor(private ngZone:NgZone) {
}
ngOnInit()
this.chart = new google.visualization.PieChart(
document.getElementById('chart_div'));
google.visualization.events.addListener(
this.chart, 'select', () => {
this.ngZone.run(() => {
this.mySelectHandler();
});
}
);
}
}
Hope that I correctly understood your question.
Thierry