I recently rewrote a small webpage in AngularJs and it was amazing how much lighter and cleaner it made the code. The conversion was mainly a case of me throwing away most of the code and adding a couple of lines of AngularJs. This was all very simple until I got to some Google Charts, at this point I had the option of leaving them as they were or converting them into AngularJs directives. I went with the directives option to keep everything in one place and work with the existing models I already have in my scope.

The next decision was whether or not to have the charts  automatically re-render when the model changes. In this case I chose not to do that as I decided flashing charts every time the model changes would be annoying to the user. If you did however choose to go this route it should be quite simple using $watch on your datatables to tell the graph when to redraw.

Take this simple page as an example

<!DOCTYPE html>
<html lang="en">
    <head>
         <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.7/angular.js" type="text/javascript"></script>
         <script src="https://www.google.com/jsapi" type="text/javascript"></script>
         <script src="main.js" type="text/javascript"></script>
         <script src="ngGoogleCharts.js" type="text/javascript"></script>
         <style type="text/css">
             .bigGraph {width:500px;height:500px;float:left;}
             .mediumGraph {width:400px;height:400px;float:left;}
             .smallGraph {width:200px;height:200px;float:left;}
         </style>
    </head>
    <body ng-controller="IndexCtrl">
        <div google-chart="PieChart" ng-model="data1" class="bigGraph"></div>
        <div google-chart="BarChart" ng-model="data2" class="mediumGraph"></div>
        <div google-chart="LineChart" ng-model="data3" class="smallGraph"></div>
    </body>
</html>

Hopefully this looks fairly simple. If you’ve used AngularJs before you might notice the absence of ng-app, this reason for this is if Angular runs before the Google Charts have loaded nothing they wont render. So I’ve had to  manually instantiate the Angular app later once Google Charts are ready.

I put the main Angular module in main.js and it’s in here where I instantiate Angular and create some hard coded datatables for the charts to run on.

 "use strict";

/*We need to manually start angular as we need to
wait for the google charting libs to be ready*/
google.setOnLoadCallback(function () {    
    angular.bootstrap(document.body, ['my-app']);
});
google.load('visualization', '1', {packages: ['corechart']});


var myApp = myApp || angular.module("my-app",["google-chart"]);

myApp.controller("IndexCtrl",function($scope){    
    $scope.data1 = {};
    $scope.data1.dataTable = new google.visualization.DataTable();
    $scope.data1.dataTable.addColumn("string","Name")
    $scope.data1.dataTable.addColumn("number","Qty")
    $scope.data1.dataTable.addRow(["Test",1]);
    $scope.data1.dataTable.addRow(["Test2",2]);
    $scope.data1.dataTable.addRow(["Test3",3]);
    $scope.data1.title="My Pie"

    $scope.data2 = {};
    $scope.data2.dataTable = new google.visualization.DataTable();
    $scope.data2.dataTable.addColumn("string","Name")
    $scope.data2.dataTable.addColumn("number","Qty")
    $scope.data2.dataTable.addRow(["Test",1]);
    $scope.data2.dataTable.addRow(["Test2",2]);
    $scope.data2.dataTable.addRow(["Test3",3]);


    $scope.data3 = {};
    $scope.data3.dataTable = new google.visualization.DataTable();
    $scope.data3.dataTable.addColumn("string","Name")
    $scope.data3.dataTable.addColumn("number","Qty")
    $scope.data3.dataTable.addRow(["Test",1]);
    $scope.data3.dataTable.addRow(["Test2",2]);
    $scope.data3.dataTable.addRow(["Test3",3]);
});

The next step was to add the logic that knows what to do with the “google-chart” attributes on the charting divs in the view. This is where Angular directives come in. I created a directive that matches on this attribute and creates the chart. In this case I put the directive in its own Angular module in a file called ngGoogleCharts.js

"use strict";

var googleChart = googleChart || angular.module("google-chart",[]);

googleChart.directive("googleChart",function(){
    return{
        restrict : "A",
        link: function($scope, $elem, $attr){
            var dt = $scope[$attr.ngModel].dataTable;
    
            var options = {};
            if($scope[$attr.ngModel].title)
                options.title = $scope[$attr.ngModel].title;

            var googleChart = new google.visualization[$attr.googleChart]($elem[0]);
            googleChart.draw(dt,options)
        }
    }
});

It’s a very simple example but should serve as a good starting point for using AngularJs directives to render Google Charts.