第十天 ReactiveCocoa - iOS开发的新框架

static void *ObservationContext = &ObservationContext;
(void)viewDidLoad {
    [super viewDidLoad];

    [LoginManager.sharedManager addObserver:self
        forKeyPath:@"loggingIn"
        options:NSKeyValueObservingOptionInitial
        context:&ObservationContext];
    [self.usernameTextField addTarget:self action:@selector(updateLogInButton)
        forControlEvents:UIControlEventEditingChanged];
    [self.passwordTextField addTarget:self action:@selector(updateLogInButton)
        forControlEvents:UIControlEventEditingChanged];
}

- (void)updateLogInButton {
    BOOL textFieldsNonEmpty = self.usernameTextField.text.length > 0 
        && self.passwordTextField.text.length > 0;
    BOOL readyToLogIn = !LoginManager.sharedManager.isLoggingIn && !self.loggedIn;
    self.logInButton.enabled = textFieldsNonEmpty && readyToLogIn;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
change:(NSDictionary *)change context:(void *)context {
    if (context == ObservationContext) {
        [self updateLogInButton];
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object
            change:change context:context];
    }
}

RAC(self.logInButton, enabled) = [RACSignal
combineLatest:@[
    self.usernameTextField.rac_textSignal,
    self.passwordTextField.rac_textSignal,
    RACObserve(LoginManager.sharedManager, loggingIn),
    RACObserve(self, loggedIn)
] reduce:^(NSString *username, NSString *password, NSNumber *
        loggingIn, NSNumber *loggedIn) {
    return @(username.length > 0 && password.length > 0 && !
            loggingIn.boolValue && !loggedIn.boolValue);
}];

// KVO
[RACObserve(self, username) subscribeNext:^(id x) {
    NSLog(@"成员变量 username 被修改成了：%@", x);
}];

// target-action
self.button.rac_command = [[RACCommand alloc] initWithSignalBlock:^RACSignal *(id input) {
    NSLog(@"按钮被点击");
    return [RACSignal empty];
}];

// Notification
[[[NSNotificationCenter defaultCenter]
rac_addObserverForName:UIKeyboardDidChangeFrameNotification
object:nil]
subscribeNext:^(id x) {
    NSLog(@"键盘Frame改变");
}
];

// Delegate
[[self rac_signalForSelector:@selector(viewWillAppear:)] subscribeNext:^(id x) {
    debugLog(@"viewWillAppear方法被调用 %@", x);
}];

-(RACSignal *)urlResults {
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        NSError *error;
        NSString *result = [NSString stringWithContentsOfURL:[NSURL URLWithString:@"http://www.devtang.com"]
            encoding:NSUTF8StringEncoding
            error:&error];
        NSLog(@"download");
        if (!result) {
            [subscriber sendError:error];
        } else {
            [subscriber sendNext:result];
            [subscriber sendCompleted];
        }
        return [RACDisposable disposableWithBlock:^{
            NSLog(@"clean up");
        }];
    }];

}

pod 'ReactiveCocoa'