iOS NSData、NSString、char *转换，简洁明了

NSData <=> NSString

    NSString *str =
@"fds";

    NSData *data = [strdataUsingEncoding:NSUTF8StringEncoding];

    str = [[NSStringalloc]initWithData:dataencoding:NSUTF8StringEncoding];

NSString <=> char *

    NSString *str =
@"fds";

    const char * aString =[strUTF8String];

    str = [NSStringstringWithUTF8String:aString];

NSData <=> char *

    char *cChar =
new char[12];

    NSData *data = [NSDatadataWithBytes:cChar
length:strlen(cChar)];

    cChar = (char *)[data
bytes];