text: //
  //  NSObject+KVOBlocks.m
  //
  //  Copyright (C) 2014 by Christopher Meyer
  //  http://schwiiz.org/
  //
  //  Permission is hereby granted, free of charge, to any person obtaining a copy
  //  of this software and associated documentation files (the "Software"), to deal
  //  in the Software without restriction, including without limitation the rights
  //  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  //  copies of the Software, and to permit persons to whom the Software is
  //  furnished to do so, subject to the following conditions:
  //
  //  The above copyright notice and this permission notice shall be included in
  //  all copies or substantial portions of the Software.
  //
  //  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  //  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  //  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  //  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  //  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  //  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  //  THE SOFTWARE.
  
  // This class is based on NSObject+KVOBlocks (MIT licensed) by Stephan Leroux.
  // See here: https://github.com/sleroux/KVO-Blocks
  
  #import "NSObject+KVOBlocks.h"
  #import <objc/runtime.h>
  
  @implementation NSObject (KVOBlocks)
  
  -(void)addObserver:(NSObject *)observer
          forKeyPath:(NSString *)keyPath
             options:(NSKeyValueObservingOptions)options
             context:(void *)context
           withBlock:(KVOBlock)block {
      
      objc_setAssociatedObject(observer, (__bridge const void *)(keyPath), block, OBJC_ASSOCIATION_COPY);
      [self addObserver:observer forKeyPath:keyPath options:options context:context];
  }
  
  -(void)removeBlockObserver:(NSObject *)observer
                  forKeyPath:(NSString *)keyPath {
      objc_setAssociatedObject(observer, (__bridge const void *)(keyPath), nil, OBJC_ASSOCIATION_COPY);
      [self removeObserver:observer forKeyPath:keyPath];
  }
  
  -(void)observeValueForKeyPath:(NSString *)keyPath
                       ofObject:(id)object
                         change:(NSDictionary *)change
                        context:(void *)context {
      
      KVOBlock block = objc_getAssociatedObject(self, (__bridge const void *)(keyPath));
      block(change, context);
  }
  
  -(void)addObserverForKeyPath:(NSString *)keyPath
                       options:(NSKeyValueObservingOptions)options
                       context:(void *)context
                     withBlock:(KVOBlock)block {
      
      [self addObserver:self forKeyPath:keyPath options:options context:context withBlock:block];
  }
  
  -(void)removeBlockObserverForKeyPath:(NSString *)keyPath {
      [self removeBlockObserver:self forKeyPath:keyPath];
  }
  
  @end