//NSData轉換為UIImage  
NSData *imageData = [NSData dataWithContentsOfFile: imagePath];  
UIImage *image = [UIImage imageWithData: imageData];  
  
//UIImage轉換為NSData  
NSData *imageData = UIImagePNGRepresentation(aimae);

1. 字符串轉Data

NSString * str =@"str"; 

NSData *data =[str dataUsingEncoding:NSUTF8StringEncoding];

2.NSData 轉NSString

NSString * str  =[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

3.data 轉char

NSData *data; 

char * haha=[data bytes]; 

4. char 轉data 

byte * byteData = malloc(sizeof(byte)*16); 

NSData *content=[NSData dataWithBytes:byteData length:16];