9></a></span></code></pre></div>
<p>Here, <code>indexOfSelectedTodo</code> depends on <code>todos.[]</code>, so it will update if we add an item
to <code>todos</code>, but won't update if the value of <code>isDone</code> on a <code>todo</code> changes.</p>
<p>Several of the <a href="https://api.emberjs.com/ember/2.18/classes/@ember%2Fobject%2Fcomputed">Ember.computed</a> macros
utilize the <code>[]</code> key to implement common use-cases. For instance, to
create a computed property that mapped properties f