title: Swift weakSelf in closure syntax
body: <p>I have this code to get JSON:</p>
  
  <pre><code>Alamofire.request(.GET, worlds).responseJSON { (request, response, JSON, error) in
          println(JSON)
          //weakSelf.serverList = JSON
      }
  </code></pre>
  
  <p>How to declare weakSelf here? I know it should be unowned in my case, but I can't find correct syntax for this. When I try use [unowned self].serverList instead of the commented line, the compiler shows me error "use of unresolved identifier 'unowned'". 
  I also tried to declare constant before block like this:</p>
  
  <pre><code>unowned let uSelf = self
  </code></pre>
  
  <p>It works like a charm, but I want to understand how to use [unowned self] in my case. </p>