If you check the documentation there's Category type which is:
typedef struct objc_category *Category;
You are getting this error because Category is defined as a pointer to struct objc_category.
If you want to avoid these kind of errors I suggest you adding your own prefix to all the classes you make in the project. Either from your name:
- Your nickname: iAsh
- ClassPrefix: IA
- Example class: IACategory
or from project name:
- Project: Awesome Project;
- Class prefix: AP
- Example class: APCategory
Also double-checking with documentation is always good. It's very rare that you'll hit existing class, but possible.
