I copied a xib (including the corresponding class) from one project to another project, but it crashed when running, saying that the unpacking was empty. But the original project is exactly the same as the newly moved project, so why does it crash? ! ! ! ! 
漂亮男人2017-05-02 09:25:55
What is returned is an optional value. You can go to xib to see its identify or see if it has been imported
大家讲道理2017-05-02 09:25:55
Please post the initialization code of nib
Your nib is completely empty