@dynamic implementation

dynamic-impl

Person.h (Person)
@interface Person : NSObject
@property (copy) NSString *givenName;
@property (copy) NSString *surname;
@end

Person.m (Person)
@interface Person ()
@property (strong) NSMutableDictionary *properties;
@end

@implementation Person
@dynamic givenName, surname;
@synthesize properties = properties_;

- (id)init {
  if ((self = [super init])) {
    properties_ = [[NSMutableDictionary alloc] init];
  }
  return self;
}

static id propertyIMP(id self, SEL _cmd) {
  return [[self properties] valueForKey:
          NSStringFromSelector(_cmd)];
}

static void setPropertyIMP(id self, SEL _cmd, id aValue) {
  id value = [aValue copy];
  
  NSMutableString *key =
  [NSStringFromSelector(_cmd) mutableCopy];
  
  // Delete “set” and “:” and lowercase first letter
  [key deleteCharactersInRange:NSMakeRange(0, 3)];
  [key deleteCharactersInRange:
                         NSMakeRange([key length] - 1, 1)];
  NSString *firstChar = [key substringToIndex:1];
  [key replaceCharactersInRange:NSMakeRange(0, 1)
                  withString:[firstChar lowercaseString]];
  
  [[self properties] setValue:value forKey:key];
}

+ (BOOL)resolveInstanceMethod:(SEL)aSEL {
  if ([NSStringFromSelector(aSEL) hasPrefix:@”set”]) {
    class_addMethod([self class], aSEL,(IMP)setPropertyIMP, “v@:@”);
  }
  else {
    class_addMethod([self class], aSEL, (IMP)propertyIMP, “@@:”);
  }
  return YES;
}