Question

我正在使用switch case语句来确定我在游戏中心多人游戏中收到的数据。

我看不出它有什么问题，但是当添加第二个案例陈述时，它就会停止工作。

我已声明：

typedef enum
{
    kPacketTypeScore,
    kPacketTypeReady,
} EPacketTypes;

typedef struct
{
    EPacketTypes type;
    size_t size;
} SPacketInfo;

typedef struct
{
    SPacketInfo packetInfo;

    int score;
} SScorePacket;

typedef struct
{
    SPacketInfo packetInfo;

    bool ready;
} SReadyPacket;

- (void)match:(GKMatch *)match didReceiveData:(NSData *)data fromPlayer:(NSString *)playerID
{
    // first, assume it's the general SPacketInfo, that way we can access type and size
    packet = (SPacketInfo*)[data bytes];

    scoreData *scoreDat = [scoreData sharedData];
    BOOL rdyReceived;

    switch (packet->type)
    {
        case kPacketTypeScore:
        {
            SScorePacket* scorePacket = (SScorePacket*)packet;

            [scoreLabel setString:[NSString stringWithFormat:@"You: %d Challenger: %d", scoreDat.score, scorePacket->score]];

            break;
        }

        case kPacketTypeReady:
        {
            SReadyPacket* readyPacket = (SReadyPacket*)packet;

            rdyReceived = readyPacket->ready;

            if (rdyReceived == FALSE && scoreDat.mpRdy == TRUE) {
                [rdyLabel setString:@"Waiting for challenger..."];
            }

            if (rdyReceived == TRUE && scoreDat.mpRdy == FALSE) {
                [rdyLabel setString:@"Challenger is waiting... Ready?"];
            }

            if (rdyReceived == TRUE && scoreDat.mpRdy == TRUE) {
                [[CCDirector sharedDirector] replaceScene:[CCTransitionFade transitionWithDuration:1.0 scene:[mpView node] withColor:ccWHITE]];
            }
            break;
        }

        default:
            CCLOG(@"received unknown packet type %i (size: %u)", packet->type, packet->size);
            break;
    }
}

Answer 1

您确定data是SReadyPacket*吗？它可能是nil或其他类型。

Answer 2

您需要澄清数据的确切内容。您最初将其视为SPacketInfo，以获取类型。然后将其转换为另外两个结构中的一个，包含 SPacketInfo，但绝对不是SPacketInfo。然后，当您尝试访问所述结构的成员时，您将访问完全未定义的位置。

packet实际上是一个数据包结构，在这种情况下你应该将你的开关更改为：

switch (packet->packetInfo->type)

或者，它是SPacketInfo，在这种情况下，您需要以其他方式获取实际的“数据包”。

切换案例陈述问题

2 个答案: