ReactiveCocoaFramework/ReactiveCocoa/RACSubscriber.h

//
//  RACSubscriber.h
//  ReactiveCocoa
//
//  Created by Josh Abernathy on 3/1/12.
//  Copyright (c) 2012 GitHub, Inc. All rights reserved.
//

#import <Foundation/Foundation.h>

@class RACCompoundDisposable;

/// Represents any object which can directly receive values from a RACSignal.
///
/// You generally shouldn't need to implement this protocol. +[RACSignal
/// createSignal:], RACSignal's subscription methods, or RACSubject should work
/// for most uses.
///
/// Implementors of this protocol may receive messages and values from multiple
/// threads simultaneously, and so should be thread-safe. Subscribers will also
/// be weakly referenced so implementations must allow that.
@protocol RACSubscriber <NSObject>
@required

/// Send the next value to subscribers.
///
/// value - The value to send. This can be `nil`.
- (void)sendNext:(id)value;

/// Send the error to subscribers.
///
/// error - The error to send. This can be `nil`.
///
/// This terminates the subscription, and invalidates the subscriber (such that
/// it cannot subscribe to anything else in the future).
- (void)sendError:(NSError *)error;

/// Send completed to subscribers.
///
/// This terminates the subscription, and invalidates the subscriber (such that
/// it cannot subscribe to anything else in the future).
- (void)sendCompleted;

/// Sends the subscriber a disposable that represents one of its subscriptions.
///
/// A subscriber may receive multiple disposables if it gets subscribed to
/// multiple signals; however, any error or completed events must terminate _all_
/// subscriptions.
- (void)didSubscribeWithDisposable:(RACCompoundDisposable *)disposable;

@end