objective c 不一样数据类型转换

1. NSString 转 byte字节

   NSData *strDataBytes = [@"$$" dataUsingEncoding:NSUTF8StringEncoding];

   转换结果为｛0x24, 0x24};

2. int 转 byte

   NSMutableData *myData = [[NSMutableData alloc] init];

   int num = 1024;

   [myData appendBytes:&num length:sizeof(num)];

3. Byte数组 转 NSData

   Byte *bytes = {***};

   NSData *strData = [NSData dataWithBytes:bytes length:strlen];
   

4. NSData 转 NSString

   NSData *strData = ***;
   

   NSString* string = [[NSString alloc] initWithData:strData encoding:NSUTF8StringEncoding];