Class extension implementation must be in the original class, what is the significance? objective-c

Question

There is a person class. Write another extension: Person_testExt.h, but only .h file. I added a - (void)run method. But the implementation still has to be in Person.m.
So if you write an extension to NSString, and if you implement this method, does it need to be in the original .m file? So what's the point of expansion?

Answer 1

You can use category