title: Can somebody give a snippet of "append if not exists" method in swift array?
body: <p>Because I use this routine a lot, can somebody create an extension method of Swift array which will detect whether if the data that is going to be appended already exists, then it's not appended? I know that it's only a matter of few code like this:</p>
  
  <pre><code>var arr = [Int]()
  for element in inputArr {
      if !arr.contains(element) { arr.append(element); }
  }
  </code></pre>
  
  <p>Becomes:</p>
  
  <pre><code>var arr = [Int]()
  for element in inputArr { arr.appendUnique(element); }
  </code></pre>
  
  <p>Or:</p>
  
  <pre><code>var arr = [String]()
  for element in inputArr {
      if !arr.contains(element) { arr.append(element); }
  }
  </code></pre>
  
  <p>Becomes:</p>
  
  <pre><code>var arr = [String]()
  for element in inputArr { arr.appendUnique(element); }
  </code></pre>
  
  <p>Same method for different element types. Frankly, from this simple code, I also want to learn on how to extend the <code>Collection</code> with variable types. It fascinates me how Array's methods can have different parameter types whenever the object was initialized with different parameter types. Array and Dictionary are two things that I still don't get how to extend them properly. Thanks.</p>