iOS Tips: Can't find a solution to import header files

introduction

Problem description: Unknown type name 'xxxx'

problem causes:

1. cache causes
2. Search Paths does not set the corresponding directory: for example, after pod install, the corresponding xcodeproj configuration is not modified
3. When creating a new file, add the file to other targets: such as accidentally adding the file to the message push extension

Solution: First analyze and find the corresponding reasons, and then solve them accordingly.

I Analyze the cause of the problem

Analysis method: The enumeration uses the corresponding enumeration type, and the class is declared with ID or c@lass.

Change the class file imported in your .h to a @class declaration, and then import it in .m. Similarly, enumerations can be declared using the corresponding enumeration type, and classes can be declared using the corresponding enumeration type.