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我正在使用ReactiveCocoa保持UICollectionView與消息列表保持最新。在我的模型收到新消息後，嘗試更新我的集合視圖時發生崩潰。NSObject（RACKVOWrapper）rac_observeKeyPath：options：observer：block：EXC_BAD_ACCESS Crash
這是我的視圖模型，它通過來自套接字客戶端的委託調用獲取更新。
@interface ConversationViewModel : NSObject
@property (nonatomic, strong) NSMutableArray *messages;
- (RACSignal *)rac_signalForMessageReceived;
@end
@implementation ConversationViewModel
....
- (void)client:(PSClient *)theClient didReceiveMessage:(PSMessage *)aMessage {
[self.messages addObject:aMessage];
[_messageReceivedSubscriber sendNext:nil];
}
....
- (RACSignal *)rac_signalForMessageReceived {
RACSignal *signal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
self.messageReceivedSubscriber = subscriber;
return [RACDisposable disposableWithBlock:^{
self.messageReceivedSubscriber = nil;
// Do Nothing
}];
}];
[signal setName:@"rac_signalForMessageReceived"];
return signal;
}
和消息對象是
@interface Message : NSObject
@property (nonatomic, assign) NSString *message;
@property (nonatomic, assign) NSString *name;
@end
這裏是控制器如何使用它。
- (void)viewDidLoad
[super viewDidLoad];
[self.conversationViewModel.rac_signalForMessageReceived subscribeNext:^(PSMessage *message) {
[self.collectionView reloadData];
}];
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return [self.conversationViewModel.messages count];
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
PSConversationMessageCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"conversationCell" forIndexPath:indexPath];
[cell setMessage:self.conversationViewModel.messages[indexPath.row]];
return cell;
}
最後，這裏是我如何做單元格內的綁定。
- (void)awakeFromNib {
RAC(self.messageLabel, text) = RACObserve(self, message.message);
RAC(self.nameLabel, text) = RACObserve(self, message.name);
}
只要收集視圖重新加載，我就會在rac_observeKeyPath中得到一個異常：options：observer：block :.在下面的屏幕截圖中可以看到堆棧。 
有誰知道爲什麼這會導致異常？或者在ConversationViewModel中處理接收消息的更好方法？