如何按创建日期查询 PFFile

Question

我正在使用此代码从 Parse 数据中检索图像...

if let userPicture = object.valueForKey("Image") as? PFFile {
      userPicture.getDataInBackgroundWithBlock({ (imageData: NSData?, error: NSError?) -> Void in
           if (error == nil) {
                let image = UIImage(data:imageData!)
                self.ImageArray.insert(image!, atIndex: 0)
           }
           else {
                self.alert("Error: \(error!) \(error!.userInfo!)", Message: "Make sure you have a secure internet connection")
           }
           dispatch_async(dispatch_get_main_queue()) {
                println("Finished Pictures")
           }
      })
 }

我正在使用此代码从 Parse 中检索字符串：

 var stuffarray = [String]()

 var query = PFQuery(className:"ClassName")
 query.findObjectsInBackgroundWithBlock {
            (objects: [AnyObject]?, error: NSError?) -> Void in

      if error == nil {
           // The find succeeded.
           println("Successfully retrieved \(objects!.count) scores.")
           // Do something with the found objects
           if let objects = objects as? [PFObject] {
                for object in objects {
                     stuffarray.append(object.valueForKey("Column")! as! String)
                }
           } else {
                // Log details of the failure
                println("Error: \(error!) \(error!.userInfo!)")
           }

           dispatch_async(dispatch_get_main_queue()) {
                self.alert("\(stuffarray)", Message: "")
           }
      }
 }

我知道如何通过添加以下代码来查询第二个示例：

query.orderByAscending("createdAt")

我的问题是，我如何查询第一个示例（图像），就像我在第二个示例中那样？我尝试使用以下代码，但出现错误：

userPicture.orderByAscending("createdAt")

我尝试使用下面的代码，文本被正确返回，但图像仍然以随机顺序返回...

var query = PFQuery(className:"Featured")
query.orderByDescending("createdAt")
query.findObjectsInBackgroundWithBlock {
    (objects: [AnyObject]?, error: NSError?) -> Void in

    if error == nil {
        // The find succeeded.
        println("Successfully retrieved \(objects!.count) Items.")
        // Do something with the found objects
        if let objects = objects as? [PFObject] {
            for object in objects {

                self.NameArray.insert(object.valueForKey("Text")! as! String, atIndex: 0)
                self.ItemNameArray.insert(object.valueForKey("ItemName")! as! String, atIndex: 0)


                let userImageFile = object["Image"] as! PFFile
                userImageFile.getDataInBackgroundWithBlock {
                    (imageData: NSData?, error: NSError?) -> Void in
                    if error == nil {
                        if let imageData = imageData {
                            let image = UIImage(data:imageData)

                            self.imageArray.insert(image!, atIndex: 0)
                        }
                    }



                    dispatch_async(dispatch_get_main_queue()) {

                        self.loading.hidden = true

                        self.collectionView.reloadData()

                    }

                }




            }


        }
    } else {
        // Log details of the failure
        println("Error: \(error!) \(error!.userInfo!)")

    }

        }

Answer 1

第一个查询出错的原因是您没有获取对象数组。您正在获取不能为 "ordered" 的单个 PFFile 的数据内容。如果您希望查询 PFFiles 列表并按创建日期对它们进行排序，则需要查询图像附加到的 Class 对象，然后为每个对象获取图像数据（最好是异步的）。有关示例，请参见下面的代码片段：

PFQuery *query = [PFQuery queryWithClassName:@"Photo"];
[query orderByDescending:@"createdAt"];

[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {

    if (!error) {
        for (PFObject *object in objects) {

            [objectIDArray addObject:object.objectId];
            NSString *postedBy = object[@"postedBy"];
            [postedByFeedArray addObject:postedBy];
            NSString *caption = object[@"caption"];
            [captionFeedArray addObject:caption];

            PFFile *file = object[@"photoFile"];
            [file getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
                if (!error) {
                    [photoFeedArray addObject:data];
                }
                dispatch_async(dispatch_get_main_queue(), ^{
                    [_activityIndicator stopAnimating];
                    [_tableView reloadData];
                });
            }];

        }
    } else {
        NSLog(@"ERROR: %@", error);
    }
}];

如果您需要帮助将其转换为 Swift，请告诉我。

Answer 2

回应，"I changed it to 'append', and the arrays images are still in a random order. the 2 other string items work perfectly. Why is it just the images. Please give an answer in swift."：

您的图片之所以仍处于随机顺序，是因为它们是从服务器异步下载的。 PFFile getDataInBackgroundWithBlock 在后台运行，较小的文件可能比较早启动的较大文件完成得更快。

在您真正准备好在 UICollectionView 或 UITableView 中显示图像之前，您不应该下载图像。当您渲染单元格时，您将调用 PFFile getDataInBackgroundWithBlock 然后并且仅在那时。

如何按创建日期查询 PFFile

How to query an PFFile By Creation Date

uiimage

ios

parse-platform

swift

ios8