[NSCFType generatePieChart]: unrecognized selector sent to instance 0x4d80b00'

因为这个纠结了许久，后来终于在http://forums.macrumors.com/showthread.php?t=895581找到了答案，

Are you sure that "self" is still a valid object once your button is clicked? It could be a memory management bug and you're releasing the object too early. Can you post more code?

Hello, sorry for not following up on this thread, I just wanted to let you know how I solved this problem: Yes I was releasing the class too early, there's a hint in the error: Code: [NSCFType generatePieChart]: unrecognized selector sent to instance 0x4d80b00' "self" class isn't called NSCFType, as a matter of fact NSCFType is an internal undocumented class in the SDK, the fact that it showed up here means the memory space of my class got freed and this was stored in its location.

大意就是NSCFType这个东西是没有在文档中提到的内部类，我想给你发送消息的类已经被释放掉了，NSCFType这个东西被存放在他原来的位置上，所以会这样提示