Low-level errors that XIB cannot drag lines.

Low-level errors that XIB cannot drag lines.
Problem description

After the XIB file is created, it is associated with the. m file, but it cannot be dragged in any way. The process does not respond. Clearing the cache and restarting Xcode cannot be solved.

Solution

In fact, this is a low-level error because the class of the view of xib is incorrect. In this case, you need to select the view of xib and click the top right corner.
Bytes
Check whether the @ interface of the Class and. m files are consistent. If they are inconsistent, click the drop-down box and select the corresponding name to drag the lines normally.