title: What is the relation between .h and .m files?
body: <p>I know that .m files are where the implementation is and .h files have the method signatures, etc. When one wants to use a certain class in his class, then he imports the .h file. Preprocessor replaces the import .h file with the content of the .h file. What I don't understand is how come access to implementation become available from just preprocessor bringing the .h content? What is the runtime mechanism that allows this? </p>