title: Creating an NSDictionary
body: <p>In the following code, the first log statement shows a decimal as expected, but the second logs NULL. What am I doing wrong?</p>
  
  <pre><code>NSDictionary *entry = [[NSDictionary alloc] initWithObjectsAndKeys:
    @"x", [NSNumber numberWithDouble:acceleration.x],
    @"y", [NSNumber numberWithDouble:acceleration.y],
    @"z", [NSNumber numberWithDouble:acceleration.z],
    @"date", [NSDate date],
    nil];
  NSLog([NSString stringWithFormat:@"%@", [NSNumber numberWithDouble:acceleration.x]]);
  NSLog([NSString stringWithFormat:@"%@", [entry objectForKey:@"x"]]);
  </code></pre>