base/ios/crb_protocol_observers.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_IOS_CRB_PROTOCOL_OBSERVERS_H_
   6 #define BASE_IOS_CRB_PROTOCOL_OBSERVERS_H_
   7
   8 #import <Foundation/Foundation.h>
   9
  10 typedef void (^ExecutionWithObserverBlock)(id);
  11
  12 // Implements a container for observers that implement a specific Objective-C
  13 // protocol. The container forwards method invocations to its contained
  14 // observers, so that sending a message to all the observers is as simple as
  15 // sending the message to the container.
  16 // It is safe for an observer to remove itself or another observer while being
  17 // notified. It is also safe to add an other observer while being notified but
  18 // the newly added observer will not be notified as part of the current
  19 // notification dispatch.
  20 @interface CRBProtocolObservers : NSObject
  21
  22 // The Objective-C protocol that the observers in this container conform to.
  23 @property(nonatomic, readonly) Protocol* protocol;
  24
  25 // Returns a CRBProtocolObservers container for observers that conform to
  26 // |protocol|.
  27 + (instancetype)observersWithProtocol:(Protocol*)protocol;
  28
  29 // Adds |observer| to this container.
  30 - (void)addObserver:(id)observer;
  31
  32 // Remove |observer| from this container.
  33 - (void)removeObserver:(id)observer;
  34
  35 // Returns true if there are currently no observers.
  36 - (BOOL)empty;
  37
  38 // Executes callback on every observer. |callback| cannot be nil.
  39 - (void)executeOnObservers:(ExecutionWithObserverBlock)callback;
  40
  41 @end
  42
  43 #endif  // BASE_IOS_CRB_PROTOCOL_OBSERVERS_H_