title: How to remove hash keys which hash value is blank?
body: <p>I am using Ruby on Rails 3.2.13 and I would like to remove hash keys which corresponding hash value is blank. That is, if I have the following hash</p>
  
  <pre><code>{ :a =&gt; 0, :b =&gt; 1, :c =&gt; true, :d =&gt; "", :e =&gt; "   ", :f =&gt; nil }
  </code></pre>
  
  <p>then the resulting hash should be (note: <code>0</code> and <code>true</code> are not considered blank)</p>
  
  <pre><code>{ :a =&gt; 0, :b =&gt; 1, :c =&gt; true }
  </code></pre>
  
  <p>How can I make that?</p>