Question

I have a scope variable $scope.first_unread_id which is defined in my controller. In my template, I have:

<div id="items" >
  <ul class="standard-list">
    <li ng-repeat="item in items" scroll-to-id="first_unread_id">
    <span class="content">{{ item.content }}</span>
    </li>
  </ul>
</div>

and my directive looks like:

angular.module('ScrollToId', []).
directive('scrollToId', function () {
  return function (scope, element, attributes) {
    var id = scope.$parent[attributes["scrollToId"]];
    if (id === scope.item.id) {
      setTimeout(function () {
        window.scrollTo(0, element[0].offsetTop - 100)
      }, 20);
    }
  }

});

it works, however, two questions:

1. Is there a better way of getting the “first_unread_id” off the controller scope into the direct than interrogating scope.$parent? This seems a bit ‘icky’. I was hoping I could pass that through the view to the direct as a parameter w/o having to repeat that on ever li element.

2. Is there a better way to avoid the need of the setTimeout() call? Without it, it works sometimes – I imagine due to difference in timing of layout. I understand the syntax I have used is defining a link function – but it isn’t clear to me if that is a pre or post-link by default – and if that even matters for my issue.

Answer 1

1. You shouldn’t need the scope.$parent – since it will inherit the value from the parent scope, and when it changes in the parent scope it will be passed down.
2. The default is a post-link function. Do you have some images or something loading that would make the page layout change shortly after initial load? Have you tried a setTimeout with no time on it, eg setTimeout(function(){})? This would make sure this would go ‘one after’ everything else is done.
3. I would also change the logic of your directive a bit to make it more general. I would make it scroll to the element if a given condition is true.

Here are those 3 changes:

html:

<div id="items" >
  <ul class="standard-list">
    <li ng-repeat="item in items" scroll-if="item.id == first_unread_id">
      <span class="content">{{ item.content }}</span>
    </li>
  </ul>
</div>

JS:

app.directive('scrollIf', function () {
  return function (scope, element, attributes) {
    setTimeout(function () {
      if (scope.$eval(attributes.scrollIf)) {
        window.scrollTo(0, element[0].offsetTop - 100)
      }
    });
  }
});