监听了每个Port对象的throwPacketBlock,所以当在Port类中,调用self.throwPacketBlock(packet, 100);时,PipelinePlumber内就可监听到,并且处理Packet流向Pipeline。 - (void)receivePacket:(id<Packet>)packet throwPacketBlock:(void(^)(id packet))block实现中,调用block就可以将packet传向下一个Pipeline是如何实现的?