when expression the <a href="api/ng/directive/ngModel">ngModel</a> directive is bound to is a non-assignable expression.</p>
<p>Examples using assignable expressions include:</p>
<pre><code>&lt;input ng-model=&quot;namedVariable&quot;&gt;
&lt;input ng-model=&quot;myObj.someProperty&quot;&gt;
&lt;input ng-model=&quot;indexedArray[0]&quot;&gt;
</code></pre>
<p>Examples of non-assignable expressions include:</p>
<pre><code>&lt;input ng-model=&quot;foo + bar&quot;&gt;
&lt;input ng-model=&quot;42&quot;&gt;
&lt;i