Do you put #import s in .h or .m files?
objective-c
Solution
You should ALWAYS `#import` other classes in your `.m` file.
If they happen to also be members of your class, you can forward declare them (by using the `@class` directive) in your `.h` file.
The reason for doing this is because when you `#import` a `.h` file, you only want to import declarations, not definitions. By using `@class` and only `#import`ing in `.m` files, you are a) reducing overhead and b) makes for cleaner code.
Another reason you should do it this way was pointed out by Matt Gallagher:
The reasoning behind forward declarations in header files is that it avoids unnecessary dependencies. i.e. Imagine B.h forward declares A and B.m imports A.h. Then imagine C.m, D.m, E.m and F.m import B.h. After all this is done, A.h changes. Since A is only forward declared in B.h, only B.m needs to rebuild. Without forward declarations, C.m, D.m, E.m and F.m would all need to be rebuild if A changes
Example:
`.h` file:
@class BarClass;
@interface FooClass : NSObject
...
@end
`.m` file
#import "BarClass.h"
@implementation FooClass
...
@end
Problem
I wonder about Objective-C style. I have FooClass.[hm] that depends on BarClass.[hm] for its implementation (though not for its interface). I can `#import "BarClass.h"` either directly in FooClass.m or indirectly through FooClass.h. I wonder about the common choice for this.