3 plist-->data-->数组/字典

 NSData *courseListData = [NSData dataWithContentsOfFile:([[NSBundle mainBundle] pathForResource:@"quiz_course_list" ofType:@"plist"])];
  if (courseListData) {
     self.coursePlist = [NSDictionary dictionaryWithPlistData:courseListData];
//dictionaryWithPlistData：该方法是yykit的方法
  }

    NSString *pathList = [[NSBundle mainBundle]pathForResource:@"ChinaRegion" ofType:@"plist"];
    NSArray *listArray = [NSArray arrayWithContentsOfFile:pathList];
    NSLog(@"%@",listArray);

4 data-->array/dictionary

      //路径文件(json)-->data
    NSString *path = [[NSBundle mainBundle]pathForResource:@"answer" ofType:@"json"];
    NSData *data = [NSData dataWithContentsOfFile:path];
    //data-->array/dictionary
    NSArray *arr = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
    NSLog(@"arr = %@",arr);

//路径文件(plist)-->data-->arr/dic
    NSString *path = [[NSBundle mainBundle]pathForResource:@"grade_list_cn" ofType:@"plist"];
    self.gradeDic = [NSDictionary dictionaryWithPlistData:[NSData dataWithContentsOfFile:path]];

5 UIimage

    //image -->data
    UIImage *image =[UIImage imageNamed:@""];
    NSData *pngData =UIImagePNGRepresentation(image);
    NSData *jpegdata = UIImageJPEGRepresentation(image, 1);//compressionQuality:压缩质量,1代表质量最高
    
    //data-->image
    NSData *imageData = [NSData dataWithContentsOfFile:@"imagePath"];
    UIImage *image1 = [UIImage imageWithData:imageData];

6加载网络图片

    //1 阻塞线程
    NSURL *url = [NSURL URLWithString:@"https://ubmcmm.baidustatic.com/media/v1/0f000nKyy1AN5J31jAVuE0.jpg"];
    NSData *urlimageData =[NSData dataWithContentsOfURL:url];
    UIImage *urlimage = [UIImage imageWithData:urlimageData];
    self.urlImageView.image = urlimage;
    //2 异步加载
    NSOperationQueue *operationQ = [[NSOperationQueue alloc]init];
    NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(downloadImage) object:nil];
    [operationQ addOperation :op];

    //3使用SDWebImage
    [imageView sd_setImageWithURL:imageUrl];
//注意：有的url有中文字符，需要进行转义
    NSString *str = @"https://upload.jianshu.io/admin_banners/web_images/4570/5d4776585f0206ff2e807971a13b06ed7d494595.jpg?imageMogr2/auto-orient/strip|imageView2/1/w/1250/h/540";
    NSString *str1 = [str stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
  [headerImageV sd_setImageWithURL:[NSURL URLWithString:str1]];