title: Trivial "+[NSTimer scheduledTimerWithTimeInterval:repeats:block:]: unrecognized selector" error
body: <p>I am banging my head against an odd error after a move to 10.12/Sierra and Xcode 8.1:</p>
  
  <pre><code>+[NSTimer scheduledTimerWithTimeInterval:repeats:block:]: 
       unrecognized selector sent to class 0x7fff78f1fa88
  </code></pre>
  
  <p>The most minimal code (default settings of create a new project) to reproduce this is:</p>
  
  <pre><code>//  AppDelegate.m
  //
  
  #import "AppDelegate.h"
  
  @interface AppDelegate ()
  
  @property (weak) IBOutlet NSWindow *window;
  @property (strong, nonatomic) NSTimer * timer;
  @end
  
  @implementation AppDelegate
  
  - (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
      self.timer = [NSTimer scheduledTimerWithTimeInterval:10 
                             repeats:YES 
                               block:^(NSTimer * _Nonnull timer) 
     {
          NSLog(@"Ping from %@", timer);
      }];
  }
  </code></pre>
  
  <p>The linking includes the (Core)Foundation classes and 'all_load'. Must be something totally trivial - but fail to what it is.</p>
  
  <p>Any and all help appreciated.</p>
  
  <p>Thanks,</p>
  
  <p>Dw.</p>