ALAsset 사용법 (시간, URL, 그림 가져오기)

    ALAsset *asset =  ;
    // 
    NSDate* pictureDate = [asset valueForProperty:ALAssetPropertyDate];
    NSDateFormatter * formatter = [[NSDateFormatter alloc]init];
    formatter.dateFormat = @"yyyy:MM:dd HH:mm:ss";
    formatter.timeZone = [NSTimeZone localTimeZone];// ， 
    NSString * pictureTime = [formatter stringFromDate:pictureDate];

    // url：
    NSURL *imageUrl = [[asset defaultRepresentation]url];

    // ：
    CGImageRef  thumbnailRef = [asset thumbnail];
    UIImage *thumbnailImg = [[UIImage alloc]initWithCGImage:thumbnailRef];

    // ：
    CGImageRef fullScreenRef = [[asset  defaultRepresentation]fullScreenImage];
    UIImage *fullScreenImg = [[UIImage alloc]initWithCGImage:fullScreenRef];

    // ：
    CGImageRef origionRef = [[asset  defaultRepresentation]fullResolutionImage];
    UIImage *origionImg = [[UIImage alloc]initWithCGImage:origionRef];