UIScrollView+RACSupport.h

//
//  UIScrollView+RACSupport.h
//  Taskworld
//
//  Created by Kittinun Vantasin on 8/5/15.
//  Copyright (c) 2015 Taskworld. All rights reserved.
//

@import UIKit;

@class RACDelegateProxy;
@class RACSignal;

@interface UIScrollView (RACSupport)

@property (nonatomic, strong, readonly) RACDelegateProxy *rac_delegateProxy;

- (RACSignal *)rac_didScroll;
- (RACSignal *)rac_didScrollHorizontally;
- (RACSignal *)rac_didScrollVertically;

@end

UIScrollView+RACSupport.m

//
//  UIScrollView+RACSupport.m
//  Taskworld
//
//  Created by Kittinun Vantasin on 8/5/15.
//  Copyright (c) 2015 Taskworld. All rights reserved.
//

@import ReactiveCocoa;
@import ObjectiveC;

#import "UIScrollView+RACSupport.h"

@implementation UIScrollView (RACSupport)

static void RACUseDelegateProxy(UIScrollView *self) {
    if (self.delegate == self.rac_delegateProxy) return;

    self.rac_delegateProxy.rac_proxiedDelegate = self.delegate;
    self.delegate = (id)self.rac_delegateProxy;
}

- (RACDelegateProxy *)rac_delegateProxy {
    RACDelegateProxy *proxy = objc_getAssociatedObject(self, _cmd);

    if (!proxy) {
        proxy = [[RACDelegateProxy alloc] initWithProtocol:@protocol(UIScrollViewDelegate)];
        objc_setAssociatedObject(self, _cmd, proxy,
                                 OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return proxy;
}

- (RACSignal *)rac_didScroll {
    RACSignal *signal = [[[[self.rac_delegateProxy signalForSelector:@selector(scrollViewDidScroll:)]
        mapReplace:self] takeUntil:self.rac_willDeallocSignal]
        setNameWithFormat:@"%@ -rac_didScroll",
                          self.rac_description];

    RACUseDelegateProxy(self);
    return signal;
}

- (RACSignal *)rac_didScrollHorizontally {
    RACSignal *signal = [[[[self.rac_delegateProxy signalForSelector:@selector(scrollViewDidScroll:)]
        reduceEach:^RACTuple *(UIScrollView *scrollView) {
            return RACTuplePack(scrollView, @(scrollView.contentOffset.x);
        }] takeUntil:self.rac_willDeallocSignal]
        setNameWithFormat:@"%@ -rac_didScrollHorizontally",
                          self.rac_description];

    RACUseDelegateProxy(self);
    return signal;
}

- (RACSignal *)rac_didScrollVertically {
    RACSignal *signal = [[[[self.rac_delegateProxy signalForSelector:@selector(scrollViewDidScroll:)]
        reduceEach:^RACTuple *(UIScrollView *scrollView) {
            return RACTuplePack(scrollView, @(scrollView.contentOffset.y);
        }] takeUntil:self.rac_willDeallocSignal]
        setNameWithFormat:@"%@ -rac_didScrollVertically",
                          self.rac_description];

    RACUseDelegateProxy(self);
    return signal;
}

@end