1，NSData 與 NSString　　NSData --> NSString　　NSString *aString = [[NSString alloc] initWithData:adata encoding:NSUTF8StringEncoding];　　NSString --> NSData　　NSString *aString = @"1234";　　NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];2，NSData 與 Byte　　NSData --> Byte　　NSString *testString = @"1234567890";　　NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];　　Byte *testByte = (Byte *)[testData bytes];　　Byte --> NSData　　Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};　　NSData *adata = [[NSData alloc] initWithBytes:byte length:24];3，NSData 與 UIImage　　NSData --> UIImage　　UIImage *aimage = [UIImage imageWithData: imageData];　　//例：從本地文件沙盒中取圖片并轉換為NSData　　NSString *path = [[NSBundle mainBundle] bundlePath];　　NSString *name = [NSString stringWithFormat:@"ceshi.png"];　　NSString *finalPath = [path stringByAppendingPathComponent:name];　　NSData *imageData = [NSData dataWithContentsOfFile: finalPath];　　UIImage *aimage = [UIImage imageWithData: imageData];　　UIImage－> NSData　　NSData *imageData = UIImagePNGRePResentation(aimae);4，NSData 與 NSMutableData　　NSData --> MSMutableData　　NSData *data=[[NSData alloc]init];　　NSMutableData *mdata=[[NSMutableData alloc]init];   　　mdata=[NSData dataWithData:data];5，NSData合并為一個NSMutableData- (NSString *)filePathWithName:(NSString *)filename {         NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);         NSString *documentsDirectory = [paths objectAtIndex:0];         return [documentsDirectory stringByAppendingPathComponent:filename]; }  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {         //音頻文件路徑         NSString *mp3Path1 = [[NSBundle mainBundle] pathForResource:@"1" ofType:@"mp3"];         NSString *mp3Path2 = [[NSBundle mainBundle] pathForResource:@"2" ofType:@"mp3"];         //音頻數據         NSData *sound1Data = [[NSData alloc] initWithContentsOfFile: mp3Path1];         NSData *sound2Data = [[NSData alloc] initWithContentsOfFile: mp3Path2];         //合并音頻         NSMutableData *sounds = [NSMutableData alloc];         [sounds appendData:sound1Data];         [sounds appendData:sound2Data];         //保存音頻          NSLog(@"data length:%d", [sounds length]);          [sounds writeToFile:[self filePathWithName:@"tmp.mp3"] atomically:YES];                  [window makeKeyAndVisible];          return YES; }