Object-c中各種資料類型之間的轉換

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：從本地檔案沙箱中取圖片並轉換為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 {         //音頻檔案路徑         NSString *mp3Path1 = [[NSBundle mainBundle] pathForResource:@"1" ofType:@"mp3"];         NSString *mp3Path2 = [[NSBundle mainBundle] pathForResource:@"2" ofType:@"mp3"];         //音頻資料         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];         //儲存音頻          NSLog(@"data length:%d", [sounds length]);          [sounds writeToFile:[self filePathWithName:@"tmp.mp3"] atomically:YES];                  [window makeKeyAndVisible];          return YES; }

6 NSString 合并

NSString* string; // 結果字串 NSString* string1, string2; //已存在的字串，需要將string1和string2串連起來 //方法1.  string = [NSString initWithFormat:@"%@,%@", string1, string2 ]; //方法2.  string = [string1 stringByAppendingString:string2]; //方法3 .  string = [string stringByAppendingFormat:@"%@,%@",string1, string2];