从NSMutableData的实例获取字节数

Question

I want to be able to determine if the number of bytes in an instance of NSMutableData is equal to zero. How would I do this?

Answer 1

Simple:

if([data length] == 0) {
  //do something
}

where data is your NSMutableData object.

NSMutableData inherits from NSData, so it gains all of the members of NSData.