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iOS Objective-C Basics (Retired) Introduction to Objective-C Composition

Posted by Mauricio Sanchez Duque
Mauricio Sanchez Duque
1,345 Points

include.h vs @class

Will there be a difference when I say to a class on top:

include "Shape.h"

than to say

@class Shape.h;

Is there a difference in functionality?

2 Answers

Alex Cevallos
Alex Cevallos
16,551 Points

Yes when you use @class Shape.h you are telling the compiler.. "Hey just make sure this class exists, but don't import it in" This method saves memory and doesn't slow down the application. @class is used inside of .h files because this way you can just check the class without using the actual methods. (Maybe you want to declare a property from a class)

When you use include "Shape.h" you are telling the compiler.. "Hey.. make sure this class exists and import everything in". This is mostly used at the top of .m files because that is where you need the imported class's methods.

Any other questions just ask! I actually asked a similar question like this on these forums a while ago.. but ask away if you need help!

Michael Bowen
Michael Bowen
770 Points

is the @class just pointing to the class in memory so the compiler knows where to grab the reference?

Alex Cevallos
Alex Cevallos
16,551 Points

Michael Bowen yup! that is essentially what it does. Points to it

Mauricio Sanchez Duque
Mauricio Sanchez Duque
1,345 Points
Mauricio Sanchez Duque
Mauricio Sanchez Duque
1,345 Points

Alex, this makes a lot of sense now! I guess from a memory usage perspective it can be handy.

Thanks!

Alex Cevallos
Alex Cevallos
16,551 Points

Mauricio,

No problem! I struggled more with the concept than you did. Good luck with your studies! Let me know if you have any more questions!