NSData* xmlData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];
NSData 转换成NSString对象NSData * data;
NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSData *data;
char *test=[data bytes];
byte* tempData = malloc(sizeof(byte)*16);
NSData *content=[NSData dataWithBytes:tempData length:16];
iOS NSString 和NSData 转换 zhuanzai
原文：http://www.cnblogs.com/jicai-ios/p/5273259.html