title: How to insert into a protobuf map in c++?
body: <p>For the following Maps unable to insert into the Map</p>
  <pre><code>map&lt;string, double&gt; doubleProps = 4;
  map&lt;string, int32&gt; intProps = 5;
  map&lt;string,string&gt; stringProps=6;
  </code></pre>
  <p>Here are the following which I have tried , but its not working</p>
  <pre><code>doubleProps[&quot;key&quot;]=&quot;value&quot; //doesn't work
  *(doubleProps[&quot;key&quot;]).insert(&quot;value&quot;) //doesn't work
  doubleProps.insert(&quot;key&quot;,&quot;value&quot;)
  </code></pre>