My extension of https://github.com/th-in-gs/THObserversAndBinders project

CXBinder.h

//
//  CXBinder.h
//  TheList
//
//  Created by Vladimir Grichina on 28.01.13.
//  Copyright (c) 2013 TheList, LLC. All rights reserved.
//

#import <THObserversAndBinders/THBinder.h>

@interface CXBinder : THBinder

@end

#define BIND(fromObj, fromPath, toObj, toPath) [CXBinder binderFromObject:fromObj keyPath:fromPath toObject:toObj keyPath:toPath]
#define BIND_T(fromObj, fromPath, toObj, toPath, transform) [CXBinder binderFromObject:fromObj keyPath:fromPath toObject:toObj keyPath:toPath transformationBlock:^id(id value) { return transform; }]

CXBinder.m

//
//  CXBinder.m
//  TheList
//
//  Created by Vladimir Grichina on 28.01.13.
//  Copyright (c) 2013 TheList, LLC. All rights reserved.
//

#import "CXBinder.h"

@interface THBinder(private)

- (id)initForBindingFromObject:(id)fromObject keyPath:(NSString *)fromKeyPath
                      toObject:(id)toObject keyPath:(NSString *)toKeyPath
           transformationBlock:(THBinderTransformationBlock)transformationBlock;

@end

@implementation CXBinder

- (id)initForBindingFromObject:(id)fromObject keyPath:(NSString *)fromKeyPath
                      toObject:(id)toObject keyPath:(NSString *)toKeyPath
           transformationBlock:(THBinderTransformationBlock)transformationBlock
{
    if (self = [super initForBindingFromObject:fromObject keyPath:fromKeyPath
                               toObject:toObject keyPath:toKeyPath
                    transformationBlock:transformationBlock]) {
        if (transformationBlock) {
            [toObject setValue:transformationBlock([fromObject valueForKeyPath:fromKeyPath])
                    forKeyPath:toKeyPath];
        } else {
            [toObject setValue:[fromObject valueForKeyPath:fromKeyPath]
                    forKeyPath:toKeyPath];
        }
    }

    return self;
}

- (void)dealloc
{
    [self stopBinding];
}

@end