javascript - AngularJS multiple expressions concatenating in interpolation with a URL

Question

I know this is long, but please bear with me. The problem is easy to understand, just takes some writing to fully explain it.

Right now I'm getting this error

Error: [$interpolate:noconcat] Error while interpolating: 
Strict Contextual Escaping disallows interpolations that concatenate multiple expressions when a trusted value is required.  
See http://docs.angularjs.org/api/ng.$sce

I've done all the reading in the documentation, but I still can't find a workaround for my problem.

I'm using $http.get on a private online source that has data that is similar to the form of a json file (so I can't modify the data). The data looks like this:

...
"items": [
  {
   "kind": "youtube#searchResult",
   "etag": ""N5Eg36Gl054SUNiWWc-Su3t5O-k/A7os41NAa_66TUu-1I-VxH70Rp0"",
   "id": {
      "kind": "youtube#video",
      "videoID": "MEoSax3BEms"
      },
   },
   {
    "kind": "youtube#searchResult",
    "etag": ""N5Eg36Gl054SUNiWWc-Su3t5O-k/VsH9AmnQecyYBLJrl1g3dhewrQo"",
    "id": {
       "kind": "youtube#video",
       "videoID": "oUBqFlRjVXU"
       },
    },
...

I'm trying to interpolate the videoId of each item into my HTML iframe that embeds the YouTube video. In my controller.js file, I'm setting the promise object after the $http.get as such

$http.get('privatesource').success(function(data) {
  $scope.videoList = data.items;
});

So now the variable "$scope.videoList" is mapped to data.items, which has a lot of video elements. In my HTML file, I can retrieve the videoID of each video by using

<ul class="videos">
  <li ng-repeat="video in videoList">
    <span>{{video.id.videoID}}</span>
  </li>
</ul>

and this lists all the videoID's. But if I try to concatenate these values to a URL, like https://youtube.com/embed/, it does not work.

<div ng-repeat="video in videoList">
    <iframe id="ytplayer" type="text/html" width="640" height="360" 
     ng-src="https://www.youtube.com/embed/{{video.id.videoId}}" 
     frameborder="0" allowfullscreen></iframe>
</div>

Is there a way that I can get the videoID to be interpolated into the youtube URL? I've tried whitelisting by using the $sceDelegateProvider as follows but it still does not work

$sceDelegateProvider.resourceUrlWhitelist([
  'self',
  'https://www.youtube.com/**']);

Any help is appreciated. Thanks!

Answer 1

An alternative to @tasseKATT's answer (which doesn't require a controller function) is to use string concatenation directly in the expression a filter:

angular.module('myApp')
  .filter('youtubeEmbedUrl', function ($sce) {
    return function(videoId) {
      return $sce.trustAsResourceUrl('http://www.youtube.com/embed/' + videoId);
    };
  });

<div ng-src="{{ video.id.videoId | youtubeEmbedUrl }}"></div>

I've found this particularly useful when using SVG icon sprites, which requires you to use the xlink:href attribute on the SVG use tag - this is subject to the same SCE rules. Repeating the controller function everywhere I needed to use a sprite seemed silly so I used the filter method instead.

angular.module('myApp')
  .filter('svgIconCardHref', function ($sce) {
    return function(iconCardId) {
      return $sce.trustAsResourceUrl('#s-icon-card-' + iconCardId);
    };
  });

<svg><use xlink:href="{{ type.key | svgIconCardHref }}"></use></svg>

Note: I had previously tried just simple string concatenation inside the expression. However this led to some unexpected behaviour where the browser would interpret the expression before Angular had a chance to parse it and replace with the real href. Since there is no ng-src equivalent for the use tag's xlink:href I opted for the filter, which seems to have solved the issue.