Private, protected and public properties in objective-c

DataObject.h

@interface DataObject : NSObject

// public properties

@end

DataObject.m

#import "DataObject.h"
#import "DataObjectSubclass.h"

@interface DataObject ()

// private properties
// + you must redclare all properties you declared in DataObjectSubclass.h

@end

@implemenation

// code

@end

DataObjectSubclass.h

#import "DataObject.h"

@interface DataObject (SubclassEyesOnly)

// protected properties

@end

ImageObject.h

#import "DataObject.h"

@interface ImageObject : DataObject

// public properties

@end

ImageObject.m

#import "DataObject.h"
#import "DataObjectSubclass.h"

@interface DataObject ()

// private properties

@end

@implemenation

// code

@end