Question

我目前正与CBPeripheralDelegate合作，在iOS设备和蓝牙低功耗USB加密狗之间交换消息。我必须实现使用串行仿真服务写入数据字节的sendMessage:方法。此方法必须在此时发送一个15字节（或更少）的帧，在发送下一个之前等待来自加密狗的确认。

以下是我的代码：

- (void)sendMessage:(NSData *)message {
    NSArray *chuncks = [self splitMessage:message];
    for (NSUInteger i = 0; i < chunks.count; i++) {
        NSData *chunk = [chunks objectAtIndex:i];
        [self sendChunk:chunk withId:i ofChunks:chances.count];
        // Wait for the ack to be received
    }
}

- (void)sendChunk:(NSData *)chunk withId:(NSInteger)id ofChunks:(NSInteger)count {
    NSMutableData *frame = [NSMutableData new];
    // Here I build my frame, adding header, current chunk ID and total number of chunks, then I call...
    [serialEmulationService writeValue:frame forCharacteristic:serialEmulationServiceCharacteristic type:CBCharacteristicWriteWithResponse];
}

现在问题是：for方法中的sendMessage:循环必须被阻止，直到外围设备无法收到确认，可能会超时。这个ack是在委托方法- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(nonnull CBCharacteristic *)characteristic error:(nullable NSError *)error中收到的，所以在这里我必须重新启动之前被阻止的for循环。

这种特殊情况的最佳做法是什么？我想使用GCD的信号量，但我无法弄清楚如何实现同步调用，无法理解解释这种技术的许多在线示例。

有人可以帮我一把吗？

Answer 1

如何完全跳过for循环...

@property (nonatomic) NSMutableArray *chunks;
@property (nonatomic) NSInteger chunkId;

- (void)sendMessage:(NSData *)message {
    self.chunks = [[self splitMessage:message] mutableCopy];
    self.chunkId = 0;

    [self sendNextChunk];
}

- (void sendNextChunk {

   NSData * chunk = self.chunks.firstObject;

   if chunk == nil  {
      return 
   }

   [self.chunks removeObjectAtIndex: 0];
   [self sendChunk:chunk withId:chunkId++ ofChunks:chances.count];
}    


- (void)sendChunk:(NSData *)chunk withId:(NSInteger)id ofChunks:(NSInteger)count {
    NSMutableData *frame = [NSMutableData new];
    // Here I build my frame, adding header, current chunk ID and total number of chunks, then I call...
    [serialEmulationService writeValue:frame forCharacteristic:serialEmulationServiceCharacteristic type:CBCharacteristicWriteWithResponse];
}

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(nonnull CBCharacteristic *)characteristic error:(nullable NSError *)error {
    [self sendNextChunk];
}

Answer 2

方法是使用Notification。创建separate method以运行for loop。此方法将Notification delegate内部的Notification方法观察sendMessage:。在linecache.checkcache('outS.txt')继续将消息添加到属性。

阻止for循环，直到委托方法被触发

2 个答案: