NSObject+KVO_Blocks.m

//
//  NSObject+KVO_Blocks.m
//
//  Created by Jonathan Annett on 1/11/13.
//  Copyright (c) 2013 Sophtwhere. All rights reserved.
//

#import "NSObject+KVO_Blocks.h"
#import "NSObject+arcAgnostics.h"
#import <objc/runtime.h>

@implementation NSObject (KVOBlocks)

- (void)addObserverForKeyPath:(NSString *)keyPath
                      options:(NSKeyValueObservingOptions)options
                      context:(void *)context
                    withBlock:(KVOBlock)block
{
    CFTypeRef key = CFBridgingRetain(keyPath);
    NSMutableArray *observers =   (__bridge NSMutableArray*) objc_getAssociatedObject(self, key);

    if (observers) {
        [observers addObject:Block_copy(block)];
    } else {
        observers = [[NSMutableArray alloc] initWithObjects:Block_copy(block), nil];
        objc_setAssociatedObject(self, key, (__bridge NSMutableArray*) observers, OBJC_ASSOCIATION_ASSIGN);
    }
    [self addObserver:self forKeyPath:keyPath options:options context:context];
    CFBridgingRelease(key);
}

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{

    CFTypeRef key = CFBridgingRetain(keyPath);
    NSMutableArray *observers =   (__bridge NSMutableArray*) objc_getAssociatedObject(self, key);
    CFBridgingRelease(key);

    if (observers) {
        NSInteger ix = 0;
        while (ix < observers.count) {
            KVOBlock locateBlock =  [observers objectAtIndex:ix];
            locateBlock(keyPath,[(id)self objectForKey:keyPath],change,context);
            ix ++;
        }
    }
}

- (void)removeBlock:(KVOBlock)block observerForKeyPath:(NSString *)keyPath
{
    CFTypeRef key = CFBridgingRetain(keyPath);
    NSMutableArray *observers =   (__bridge NSMutableArray*) objc_getAssociatedObject(self, key);
    CFBridgingRelease(key);
    if (observers) {
        if (block) {
            NSInteger ix = 0;
            while (ix < observers.count) {
                KVOBlock locateBlock =  [observers objectAtIndex:ix];
                if (locateBlock==block) {
                    Block_release(locateBlock);
                    [observers removeObjectAtIndex:ix];
                } else {
                    ix ++;
                }
            }

        } else {

            while (observers.count>0) {
                KVOBlock locateBlock = observers.lastObject;
                Block_release(locateBlock);
                [observers removeLastObject];
            }
        }

        if (observers.count==0) {
            objc_setAssociatedObject(self,key, nil, OBJC_ASSOCIATION_COPY);
            [self removeObserver:self forKeyPath:keyPath];
            [observers release];
        }
    } else {
        [self removeObserver:self forKeyPath:keyPath];
    }
    CFBridgingRelease(key);

}

@end