title: Swift - weak self in didSet
body: <p>I rarely see people using <code>[weak self]</code> in <code>didSet</code>. Is there a reason for this?</p>
  
  <p>I tried to use <code>[weak self]</code> in my <code>didSet</code> of a variable:</p>
  
  <pre><code>var data: Dictionary&lt;String, Any&gt;! { // [1]
          didSet { [2]
              self?.layoutSubviews()
          }
      }
  </code></pre>
  
  <p>Either I put <code>[weak self] in</code> at [1] or [2], I still get the error: <code>Use of unresolved identifier weak</code></p>
  
  <p>Why is that? Is it illegal to use <code>[weak self]</code> for a <code>didSet</code> ?</p>
  
  <p>Regards,</p>