Html – Compiling dynamic HTML strings from database

angularjscompilationdomdynamichtml

The Situation

Nested within our Angular app is a directive called Page, backed by a controller, which contains a div with an ng-bind-html-unsafe attribute. This is assigned to a $scope var called 'pageContent'. This var gets assigned dynamically generated HTML from a database. When the user flips to the next page, a called to the DB is made, and the pageContent var is set to this new HTML, which gets rendered onscreen through ng-bind-html-unsafe. Here's the code:

Page directive

angular.module('myApp.directives')
    .directive('myPage', function ($compile) {

        return {
            templateUrl: 'page.html',
            restrict: 'E',
            compile: function compile(element, attrs, transclude) {
                // does nothing currently
                return {
                    pre: function preLink(scope, element, attrs, controller) {
                        // does nothing currently
                    },
                    post: function postLink(scope, element, attrs, controller) {
                        // does nothing currently
                    }
                }
            }
        };
    });

Page directive's template ("page.html" from the templateUrl property above)

<div ng-controller="PageCtrl" >
   ...
   <!-- dynamic page content written into the div below -->
   <div ng-bind-html-unsafe="pageContent" >
   ...
</div>

Page controller

angular.module('myApp')
  .controller('PageCtrl', function ($scope) {

        $scope.pageContent = '';

        $scope.$on( "receivedPageContent", function(event, args) {
            console.log( 'new page content received after DB call' );
            $scope.pageContent = args.htmlStrFromDB;
        });

});

That works. We see the page's HTML from the DB rendered nicely in the browser. When the user flips to the next page, we see the next page's content, and so on. So far so good.

The Problem

The problem here is that we want to have interactive content inside of a page's content. For instance, the HTML may contain a thumbnail image where, when the user clicks on it, Angular should do something awesome, such as displaying a pop-up modal window. I've placed Angular method calls (ng-click) in the HTML strings in our database, but of course Angular isn't going to recognize either method calls or directives unless it somehow parses the HTML string, recognizes them and compiles them.

In our DB

Content for Page 1:

<p>Here's a cool pic of a lion. <img src="lion.png" ng-click="doSomethingAwesone('lion', 'showImage')" > Click on him to see a large image.</p>

Content for Page 2:

<p>Here's a snake. <img src="snake.png" ng-click="doSomethingAwesone('snake', 'playSound')" >Click to make him hiss.</p>

Back in the Page controller, we then add the corresponding $scope function:

Page controller

$scope.doSomethingAwesome = function( id, action ) {
    console.log( "Going to do " + action + " with "+ id );
}

I can't figure out how to call that 'doSomethingAwesome' method from within the HTML string from the DB. I realize Angular has to parse the HTML string somehow, but how? I've read vague mumblings about the $compile service, and copied and pasted some examples, but nothing works. Also, most examples show dynamic content only getting set during the linking phase of the directive. We would want Page to stay alive throughout the life of the app. It constantly receives, compiles and displays new content as the user flips through pages.

In an abstract sense, I guess you could say we are trying to dynamically nest chunks of Angular within an Angular app, and need to be able to swap them in and out.

I've read various bits of Angular documentation multiple times, as well as all sorts of blog posts, and JS Fiddled with people's code. I don't know whether I'm completely misunderstanding Angular, or just missing something simple, or maybe I'm slow. In any case, I could use some advice.

Best Answer

ng-bind-html-unsafe only renders the content as HTML. It doesn't bind Angular scope to the resulted DOM. You have to use $compile service for that purpose. I created this plunker to demonstrate how to use $compile to create a directive rendering dynamic HTML entered by users and binding to the controller's scope. The source is posted below.

demo.html

<!DOCTYPE html>
<html ng-app="app">

  <head>
    <script data-require="angular.js@1.0.7" data-semver="1.0.7" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.7/angular.js"></script>
    <script src="script.js"></script>
  </head>

  <body>
    <h1>Compile dynamic HTML</h1>
    <div ng-controller="MyController">
      <textarea ng-model="html"></textarea>
      <div dynamic="html"></div>
    </div>
  </body>

</html>

script.js

var app = angular.module('app', []);

app.directive('dynamic', function ($compile) {
  return {
    restrict: 'A',
    replace: true,
    link: function (scope, ele, attrs) {
      scope.$watch(attrs.dynamic, function(html) {
        ele.html(html);
        $compile(ele.contents())(scope);
      });
    }
  };
});

function MyController($scope) {
  $scope.click = function(arg) {
    alert('Clicked ' + arg);
  }
  $scope.html = '<a ng-click="click(1)" href="#">Click me</a>';
}
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