title: Modifying model's observed properties in action Ember
body: <p>I have a search results page with the retrieved search results stored in the model as results. on the same page, I have a button to check all the results for extraction.</p>
  
  <p>I have a property named checked and initially, it is set to <code>false</code>in the button action I want to change this property on each result to true.</p>
  
  <p>this is my action </p>
  
  <pre><code>checkAll(){
        this.controller.get("model.results").map(doc=&gt;{
          doc.checked = true;
        })
      }
  </code></pre>
  
  <p>but I keep getting this error:</p>
  
  <blockquote>
    <p>Assertion Failed: You must use Ember.set() to set the <code>checked</code> property (of [object Object]) to <code>true</code>.</p>
  </blockquote>
  
  <p>I don't how to use <code>Ember.set()</code> only on that property. and I don't know if this is the right way to go about this as I'm new to ember.</p>
  
  <p>any help would be much appreciated.
  Thank you.</p>