NS数据类型转换

1，NSData 与 NSString

　　NSData --> NSString

　　NSString *aString = [[NSString alloc] initWithData:adata encoding:NSUTF8StringEncoding];

　　NSString --> NSData

　　NSString *aString = @"1234";

　　NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];

2，NSData 与 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 与 UIImage

NSData --> UIImage

　　UIImage *aimage = [UIImage imageWithData: imageData];

　　//例：从本地文件沙盒中取图片并转换为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 与 NSMutableData

NSData --> MSMutableData

NSData *data=[[NSData alloc]init];

NSMutableData *mdata=[[NSMutableData alloc]init];   

mdata=[NSData dataWithData:data];

5,NSData 与NSDictionary

NSData *data =    [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:nil];

NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers  error:nil];

6，NSData合并为一个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 {    

     //音频文件路径

         NSString *mp3Path1 = [[NSBundle mainBundle] pathForResource:@"1" ofType:@"mp3"];

         NSString *mp3Path2 = [[NSBundle mainBundle] pathForResource:@"2" ofType:@"mp3"];

         //音频数据

         NSData *sound1Data = [[NSData alloc] initWithContentsOfFile: mp3Path1];

         NSData *sound2Data = [[NSData alloc] initWithContentsOfFile: mp3Path2];

         //合并音频

         NSMutableData *sounds = [NSMutableData alloc];

         [sounds appendData:sound1Data];

         [sounds appendData:sound2Data];

         //保存音频

         NSLog(@"data length:%d", [sounds length]);

         [sounds writeToFile:[self filePathWithName:@"tmp.mp3"] atomically:YES];

         [window makeKeyAndVisible];

     return YES;

 }