title: Flutter - How to count data based on ID in List
body: <p>I have a <code>List&lt;Comment&gt;</code> from all foods.</p>
  
  <pre><code>[
   {
     comment_id: '...'
     food_id: '...'
     comment: '...'
   }, 
   {
     comment_id: '...'
     food_id: '...'
     comment: '...'
   },
  
    ....
  
  ]
  </code></pre>
  
  <p>I want to know how to count the number of comments based on <code>food_id</code> in Flutter?
  Any answer is very helpful.</p>