Monkey-Patching iOS with Objective-C Categories Part II: Adding Properties

MyClassWithFakePrivateProperties.m

#import "MyClassWithFakePrivateProperties.h"

@interface MyClassWithFakePrivateProperties ()

@property (nonatomic, strong) NSString *foo;

@end

@implementation MyClassWithFakePrivateProperties

@synthesize foo;

@end

UIViewController_TourGuide.h

#import <UIKit/UIKit.h>

@interface UIViewController (TourGuide)

@property (nonatomic, retain) NSArray* tourSteps;

- (void) displayTour;

@end

UIViewController_TourGuide.m

#import "UIViewController_TourGuide.h"

static char tourStepsKey;

@implementation UIViewController (TourGuide)

- (void) setTourSteps:(NSArray*)tourSteps {
  objc_setAssociatedObject(self, &tourStepsKey,
    tourSteps, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSArray*) getTourSteps {
  return objc_getAssociatedObject(self, &tourStepsKey);
}

- (void) displayTour {
  // run the tour
}

@end

UIViewController_TourGuide_BadImplementation.m

#import "UIViewController_TourGuide.h"

@implementation UIViewController (TourGuide)

@synthesize tourSteps = tourSteps_

- (void) displayTour {
  // run the tour
}

@end

UIViewController_TourGuide_BadImplementation2.m

#import <UIKit/UIKit.h>

@interface UIViewController (TourGuide) {

@private
NSArray* _tourSteps;

}

@property (nonatomic, retain) NSArray* tourSteps;

- (void) displayTour;

@end