Hide instance variable from header file in Objective C

Question

I came across a library written in Objective C (I only have the header file and the .a binary). In the header file, it is like this:

@interface MyClass : MyS         


        

Answer 1

How about a macro trick?

Have tested code below

• have tested with dylibs - worked fine
• have tested subclassing - Warning! will break, I agree this makes the trick not that useful, but still I think it tells some about how ObjC works...

MyClass.h

@interface MyClass : NSObject {
#ifdef MYCLASS_CONTENT
    MYCLASS_CONTENT // Nothing revealed here
#endif
}
@property (nonatomic, retain) NSString *name;
@property (nonatomic, assign) int extra;
- (id)initWithString:(NSString*)str;
@end

MyClass.m

// Define the required Class content here before the #import "MyClass.h"
#define MYCLASS_CONTENT \
  NSString *_name; \
  int _extra; \
  int _hiddenThing; 

#import "MyClass.h"

@implementation MyClass
@synthesize name=_name;
@synthesize extra=_extra;

- (id)initWithString:(NSString*)str
{
    self = [super init];
    if (self) {
        self.name = str;
        self.extra = 17;
        _hiddenThing = 19;
    }
    return self;
}

- (void)dealloc
{
    [_name release];
    [super dealloc];
}

@end