objective-c - 如何从 parse.com 检索图像

Question

嗨，我是使用 parse.com 的新手实际上我正在尝试将图像保存在 parse.com 中并重新检索它。但我成功地将图像保存为PFFile

在 parse.com 仪表板中显示如下

现在我如何检索图像并在 UIImageView 中显示

我试过这样但它不起作用..

 PFQuery *query = [PFQuery queryWithClassName:@"UserPhoto"];
    [query whereKey:@"userName" containsString:@"ravi"];
    [query getObjectInBackgroundWithId:@"ID" block:^(PFObject *object, NSError *error) {
        if(!error){
            PFFile *im = [object objectForKey:@"imageFile"];
            _getImg.image = im;
        }}];

在这里，我想检索特定图像userName ravi

Answer 1

要检索图像，您需要：

1. 查询有PFObject问题的
2. 用于-[PFFile getDataInBackgroundWithBlock:]检索PFFile的数据

3. UIImage用结果创建一个NSData

   PFQuery *query = [PFQuery queryWithClassName:@"UserPhoto"];
   
   [query whereKey:@"userName" containsString:@"ravi"];
   
   [query getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) {
       if (!object) {
           return NSLog(@"%@", error);
       }
   
       PFFile *imageFile = object[@"imageFile"];
   
       [imageFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
           if (!data) {
               return NSLog(@"%@", error);
           }
   
           // Do something with the image
           self.imageView.image = [UIImage imageWithData:data];
       }];
   }];
   

顺便说一句，除非纯粹是为了实验，或者您正在主线程之外执行一些操作，否则我会避免保存PFObject同步使用-[PFObject save]和使用异步版本，-[PFObject saveInBackgroundWithBlock:].

Answer 2

You cannot use getObjectInBackgroundWithId: method in your case. Instead you can use getFirstObjectInBackgroundWithBlock: method to retrieve the first instance.