title: Lexical or Preprocessor Issue error causing Core data class "may not respond to" method warnings?
body: <p>I get <code>Lexical or Preprocessor Issue 'Group.h' file not found</code> which I believe is causing the issues below.</p>
  
  <p>I'm trying to call a method on one of my core data class instances and I get a <code>'Group' may not respond to '-addPeople:'</code> warning. But I do have an addPeople method in my XCode generated Group class, and here it is:</p>
  
  <pre><code>- (void)addPeople:(NSSet *)value {    
      [self willChangeValueForKey:@"people" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value];
      [[self primitiveValueForKey:@"people"] unionSet:value];
      [self didChangeValueForKey:@"people" withSetMutation:NSKeyValueUnionSetMutation usingObjects:value];
  }
  </code></pre>
  
  <p>I also get the same warning if I try to <code>removePeople</code>. Both of these methods have to do with NSSets but I'm able to call my setters from the Group class just fine. </p>
  
  <pre><code>[selectedObject setTitle:[[titleCell textField] text]]; // works
  [selectedObject setSubtitle:[[subTitleCell textField] text]]; // works
  NSSet *tempPeople = [NSSet setWithArray:people];
  [selectedObject addPeople:tempPeople]; // works, but with warning
  </code></pre>
  
  <p><strong>Side note</strong></p>
  
  <p>When I type <code>[selectedObject</code> I don't get autocompletion, although the word selectedObject does autocomplete as a Group. So at least that's good.</p>
  
  <p><strong>Group.h</strong></p>
  
  <pre><code>@class People;
  
  @interface Group : NSManagedObject {
  @private
  }
  @property (nonatomic, retain) NSString * title;
  @property (nonatomic, retain) NSNumber * order;
  @property (nonatomic, retain) NSString * subtitle;
  @property (nonatomic, retain) NSSet* people;
  @end
  </code></pre>
  
  <p><strong>Updated</strong></p>
  
  <p>I just finished making a new UITableViewCell class and now instead of it saying <code>Lexical or Preprocessor Issue 'Group.h' file not found</code> it now says <code>Lexical or Preprocessor Issue 'PersonCell.h' file not found</code></p>