angularjs directive api

suppose you're using angular and you have a directive that you pass data to:

<my-chart data="chartData"></my-chart>

suppose the directive needs to perform some logic when data changes. you'll probably use $watch:

angular.module('app')
.controller('MainController', function($scope){
    function dataChange(){
        $scope.chartData= {...};
    }
})
.directive('myChart', function(){
    return {
        scope: {data: '='},
        link: function(scope){
            function redraw(){...}
            scope.$watch('data', redraw);
        }
    };
});

the problem with this solution is that it's dependent on angular's $digest loop.

here is a way to invoke the directive's redraw() directly from the controller:

angular.module('app')
.controller('MainController', function($scope){
    $scope.chartApi= {};//empty object
    function dataChange(){
        $scope.chartData = {...};
        $scope.chartApi.redraw();
    }
})
.directive('myChart', function(){
    return {
        scope: {data: '=', api: '='},
        link: function(scope){
            function redraw(){...}
            scope.api.redraw = redraw;
        }
    };
});

and in html:

<my-chart data="chartData" api="chartApi"></my-chart>