title: What's the difference between "as?", "as!", and "as"?
body: <p>Before I upgraded to Swift 1.2, I could write the following line:</p>
  
  <pre><code>if let width = imageDetails["width"] as Int?
  </code></pre>
  
  <p>Now it forces me to write this line:</p>
  
  <pre><code>if let width = imageDetails["width"] as! Int?
  </code></pre>
  
  <p>My question is, if I'm forced to write it as above, couldn't I just write the code below and it would do the same thing?  Would it give me the same result in all values of imageDetails?</p>
  
  <pre><code>if let width = imageDetails["width"] as Int
  </code></pre>