title: CoreData attribute access issue
body: <p>Today I have added an attribute for the model, but I can't access the attribute:
  The model schema:</p>
  
  <pre><code>@implementation NewsContent
  
  @dynamic content;
  @dynamic contentId;
  @dynamic mediaUrl;
  @dynamic peakNum;
  @dynamic news;
  
  @end
  </code></pre>
  
  <p>I just called the <code>NSLog(@"%@", self.news.content.peakNum);</code>, but I got an error:</p>
  
  <pre><code>*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NewsContent peakNum]: unrecognized selector sent to instance 0x8359490'
  *** First throw call stack:
  (0x1e72052 0x3a06d0a 0x1e73ced 0x1dd8f00 0x1dd8ce2 0x283c8 0x1ef91 0x93336a 0xa65a5d8 0x934956 0x1dd851d 0x1dd8437 0x1e0349a 0x2274aff 0x1dd90c9 0x1dd8ce2 0x1dd851d 0x1dd8437 0x2e14ae3 0x2e15115 0x1e4697f 0x1da9b73 0x1da9454 0x1da8db4 0x1da8ccb 0x2004879 0x200493e 0x77ca9b 0x34c0 0x2ce5)
  terminate called throwing an exceptionCurrent language:  auto; currently objective-c:
  </code></pre>