NSData和结构体struct之间如何转换

NSData和结构体struct之间如何转换   

 

 

用处是当用NSNotification传递数据时需要这个转换，然后把NSData放到userInfo中。

// make a NSData object 
NSData *myData = [NSData dataWithBytes:&myPacketJoin length:sizeof(myPacketJoin)]; 

// make a new PacketJoin 
PacketJoin newJoin; 
[myData getBytes:&newJoin length:sizeof(newJoin)];

 

struct msg { 
        uint32_t msgtype;
        uint32_t param1;
        uint32_t param2;
    };
    struct msg a;
    
    a.msgtype = 123456;
    a.param1 = 12345;
    a.param2 = 12345;
   
    
    struct msg ba;
    NSData *msgData = [[NSData alloc]initWithBytes:&a length:sizeof(a)];
    [msgData getBytes:&ba length:sizeof(ba)];
    
    
    NSLog(@"a:%u", ba.msgtype);
    NSLog(@"ba:%u", a.msgtype );