After Xcode was upgraded to 12, the original Swift framework was added to the OC project. Although the -Swift file can be imported, the class declared internally by -Swift cannot be found on the simulator, so it can be used on a real machine. After a long groping, I found a solution:

1. First, make sure that the framework of Swift includes the simulator architecture. Xcode 12 has changed the default architecture of the simulator, and there are many solutions on the Internet, so I won't go into details here.

2. Create an empty swift static library project with Xcode, then add all Swift files in the original static library and edit a new static library, which can be solved.