Controller的定义是一致的，怎么还提示找不到的错呢。
2014-03-19 22:30:04.142 TestCombobox[1871:60b] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Could not load NIB in bundle: 'NSBundle </Users/hengchengfei/Library/Application Support/iPhone Simulator/7.1-64/Applications/EB6B36F9-A5B9-4BD7-B969-66959B14287E/TestCombobox.app> (loaded)' with name 'DetailViewController' and directory 'MainStoryboard.storyboardc''
------解决方案--------------------
不要把controller定义为局部变量。这样方法执行完了，会被释放掉。
一种解决办法：把controller定义为类变量。