NSMutableData如何工作？

Question

我有一个问题与NSMutableData一起使用。

我定义了一个NSMutableData *receivedData，并尝试将多个NSData*数据复制到receivedData。我刚刚调用[receivedData appendData:data]，但似乎没有复制数据：

....
NSLog(@"get data! Received %d bytes of data",[data length]);
  // output is not zero, say 1231.

[receivedData appendData:data];
NSLog(@"after append! length is %d bytes of data",[receivedData length]);
  // showing zero

感谢。

Answer 1

检查是否receivedData == nil。如果是这样，那么您可能忘记初始化它。例如：

receivedData = [[NSMutableData alloc] init];

然后在你不再需要它时释放它：

[receivedData release];
receivedData = nil;