NSObjectPropertyObservers.h

/*
 *  NSObjectPropertyObservers.h
 *
 *  Created by Nathan de Vries on 12/03/10.
 *  Copyright 2010 Nathan de Vries. All rights reserved.
 *
 */

#define OBSERVE_CHANGES_FOR_PROPERTIES(...) \
\
for (NSString* property in [NSArray arrayWithObjects:__VA_ARGS__, nil]) { \
  [self addObserver:self forKeyPath:property options:(NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld) context:NULL]; \
}

#define SYNTHESIZE_PROPERTY_CHANGE_OBSERVER() \
\
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { \
  if ([[change valueForKey:NSKeyValueChangeKindKey] integerValue] == NSKeyValueChangeSetting) { \
    \
    SEL changeSelector = NSSelectorFromString([keyPath stringByAppendingString:@"DidChange"]); \
    SEL changeSelectorWithValues = NSSelectorFromString([keyPath stringByAppendingString:@"DidChangeWithOldValue:newValue:"]); \
    \
    if ([self respondsToSelector:changeSelector]) { \
      [self performSelector:changeSelector]; \
    } else if ([self respondsToSelector:changeSelectorWithValues]) { \
      id oldValue = [change valueForKey:NSKeyValueChangeOldKey] ?: nil; \
      id newValue = [change valueForKey:NSKeyValueChangeNewKey]; \
      \
      oldValue = (oldValue == [NSNull null]) ? nil : oldValue; \
      \
      [self performSelector:changeSelectorWithValues withObject:oldValue withObject:newValue]; \
    } \
  } \
}