比如 nssting* str = @"2";转化。。。。
http://www.cnblogs.com/leipei2352/p/3722411.html
http://mobile.51cto.com/hot-404914.htm
NSString *str = @"2";NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];NSUInteger strBytes = data.length;