text: //
  //  StageSafeKVO.h
  //  Stage
  //
  //  Copyright © 2016 David Parton
  //
  //  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.
  
  #import <Foundation/Foundation.h>
  
  NS_ASSUME_NONNULL_BEGIN
  
  @interface StageSafeKVO : NSObject
  
  typedef void (^StageSafeKVOBlock)(id object, NSString* keyPath, NSDictionary* changeInfo);
  + (instancetype)observer:(id)observer watchKey:(NSString*)keyPath inObject:(id)object withBlock:(StageSafeKVOBlock)block;
  + (instancetype)observer:(id)observer watchKeys:(NSArray*)keyPaths inObject:(id)object withBlock:(StageSafeKVOBlock)block;
  
  - (void)stopObserving;
  
  @end
  
  NS_ASSUME_NONNULL_END
  