title: Dart String Interpolation - $ started variables
body: <p>How we can use a variable started with <code>$</code> in a string interpolation?</p>
  <p>What is a string interpolation equivalent of the following string concatenation?</p>
  <pre class="lang-dart prettyprint-override"><code>final String $foo = 'Foo';
  
  print('my variable is '+ $foo);
  </code></pre>
  <p>Note: it is useful when we have a variable started with <code>_</code> and want to make it public, i.e a JSON field named <code>_</code> , can be converted to <code>$_</code> in dart</p>