首先，我下描写叙述一下bug的发生情况：

在使用UIPickerView实现选择城市的时候。出现这样一个Bug

1、在iOS 6的系统上

2、Picker的数据上省份一栏选择了“香港”或者“澳门”这些没有二级数据的地区

3、然后滑动PickerView的二级选项。结果崩溃，并且不跳不论什么Delegate

4、这个问题在iOS 7或者更高系统的手机上是不存在的。

bug提示信息例如以下：

2014-07-28 19:46:00.711 BaiHe[1719:907] *** Assertion failure in -[UITableViewRowData rectForRow:inSection:], /SourceCache/UIKit/UIKit-2380.17/UITableViewRowData.m:1630

2014-07-28 19:46:00.915 BaiHe[1719:907] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'request for rect at invalid index path ( 2 indexes [0, 0])'

*** First throw call stack:

(0x340ae2a3 0x3bd2e97f 0x340ae15d 0x34983ab7 0x35ee6ffb 0x35f04919 0x3606ec63 0x3623e8ef 0x35fd923b 0x35ff26ed 0x35fd3d89 0x35f9b3f5 0x36188a39 0x35ebf82f 0x35ebe293 0x35ec91e7 0x35ec8db3 0x35eb6801 0x35eb611b 0x37ba85a3 0x37ba81d3 0x34083173 0x34083117 0x34081f99 0x33ff4ebd 0x33ff4d49 0x37ba72eb 0x35f0a301 0x399cdf 0x26370)

libc++abi.dylib: terminate called throwing an exception

找了非常久。从网上网友处看到了一个解决方式，可是我试了一下。貌似缺少了些什么，所以我把解决方式的所有代码上传，希望能够帮助遇到相同问题的朋友。

解决方式：

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
//假设当前component中相应的数组为空。推断一些假设为空，返回1
if ([[self.pickerArray objectAtIndex: component] count] <= 0)
{
return 1;
}

return \[\[self.pickerArray objectAtIndex: component\] count\];  

}

• (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
  {
  UILabel *label = (UILabel *)view;

  if (!label)
  {
  label = [[[UILabel alloc] initWithFrame: CGRectMake(0, 0, 320, 20)] autorelease];
  label.backgroundColor = [UIColor clearColor];
  label.textAlignment = UITextAlignmentCenter;
  label.adjustsFontSizeToFitWidth = YES;
  label.numberOfLines = 2;
  label.minimumFontSize = 8.0f;
  }

  label.text = [[self.pickerArray objectAtIndex: component] count] ? [[[self.pickerArray objectAtIndex: component] objectAtIndex:row] objectForKey: @"hintValue"] : @"";

  //这里加上这段推断就可以
  if ([[self.pickerArray objectAtIndex: component] count] <= 0)
  {
  label.userInteractionEnabled = NO;
  }
  else
  {
  label.userInteractionEnabled = YES;
  }

  return label;
  }