title: aggregate values from specific key in an array of hashes
body: <p>I'm trying to build an array of values that come from an array of hashes, at the moment my code looks like this:</p>
  
  <pre><code>ids = array_of_hashes.inject([]) do |result,instance|
      result &lt;&lt; instance[:id]
      result
  end
  </code></pre>
  
  <p>I just want to know if there's a more efficient way to do it?</p>