title: Check if dictionary contains value in Swift
body: <p>Just simple task. I've got a dictionary <code>var types = [Int : String]()</code> which inits like an empty and after some user actions it fills with data. According to emptiness or some specific data in this dictionary I enable/disable a button in UI. 
  Check for emptiness is easy, but how to check if dictionary contains certain value? 
  Compiler suggested me a placeholder with predicate:</p>
  
  <pre><code>types.contains(predicate: ((Int, String)) throws -&gt; Bool&gt;)
  </code></pre>