ReactiveCocoa is better than KVO and delegates

TestViewController.m

//
//  TestViewController.m
//  iOSDemo
//
//  Created by Sean Hess on 6/4/13.
//  Copyright (c) 2013 GitHub, Inc. All rights reserved.
//

#import "TestViewController.h"
#import "User.h"
#import <ReactiveCocoa/ReactiveCocoa.h>

@interface TestViewController () <UserDelegate>
@property (nonatomic, strong) User * user;
@property (nonatomic, strong) UIButton * logoutButton;
@property (nonatomic, strong) UIButton * loginButton;
@end

@implementation TestViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // 1. DELEGATES
    // problems:
    // - only one delegate allowed
    // - I don't actually "own" user
    // - events are a strange way to do this. What if there is more state?
    // - has user even been set yet??
    self.user.delegate = self;
    
    
    
    
    // 2. NOTIFICATIONS (basically the same
    // - same problems
    // - (+) now multiple listeners
    // - but this funky global notification center.
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(userDidLogin) name:@"login" object:self.user];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(userDidLogut) name:@"login" object:self.user];
    
    
    
    // 3. KVO
    // - data driven
    // - error prone: "loggedIn" string
    // - bad syntax: in 3 places. Big if/else statement
    [self.user addObserver:self forKeyPath:@"loggedIn" options:NSKeyValueObservingOptionNew context:nil];
    
    
    
    
    // 4. ReactiveCocoa
    // - user doesn't even have to be set!!
    // - great code locality
    // - don't have to use the string name of the property
    // - LOTS more great features
    [RACAble(self.user.loggedIn) subscribeNext:^(id x) {
        [self setButtonsBasedOnLogin];
    }];
}

// DELEGATES
- (void)userDidLogin {
    self.logoutButton.hidden = NO;
    self.loginButton.hidden = YES;
}

- (void)userDidLogout {
    self.logoutButton.hidden = YES;
    self.loginButton.hidden = NO;
}

// 3. IMPROVED
- (void)setButtonsBasedOnLogin {
    self.logoutButton.hidden = self.user.loggedIn;
    self.loginButton.hidden = !self.user.loggedIn;
}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if ([keyPath isEqualToString:@"loggedIn"] && object == self.user) {
        [self setButtonsBasedOnLogin];
    }
}

@end

User.h

//
//  User.h
//  iOSDemo
//
//  Created by Sean Hess on 6/4/13.
//  Copyright (c) 2013 GitHub, Inc. All rights reserved.
//

#import <Foundation/Foundation.h>

@protocol UserDelegate <NSObject>
-(void)userDidLogin;
-(void)userDidLogout;
@end

@interface User : NSObject
@property (weak, nonatomic) id<UserDelegate>delegate;
@property (nonatomic) BOOL loggedIn;
@end