ios - 转换到 UIImage 的 PFFile 数组在 for 循环之外为空

Question

我试图下载一些存储在解析服务器上的图像作为 PFFile，然后在 UIImage 中转换它们。这包含在 for 循环中，并且 UIImages 附加到数组 tempImageArray。该数组在 for 循环内填充(包含服务器上的所有 9 个图像)，但是当我尝试在 for 循环外使用该数组时，该数组为空，返回 []。

这是否与 getdatainbackground 有关，而 swift 在我可以使用数组 tempImagesArray 之前跳过了它？

整个 block 的代码如下。

let packQuery = PFQuery(className: "Pack")

packQuery.findObjectsInBackground(block: { (objectsArray, error) in
    if error != nil {
        print(error!)
    } else if let packs = objectsArray {
        var tempImageArray = [UIImage]()
        for object in packs {
            if object.object(forKey: "file") != nil {
                var imageDataDownLoad = object["file"] as! PFFile
                    imageDataDownLoad.getDataInBackground(block: { (imageData, error) in
                        if error == nil {
                            if let image = UIImage(data: imageData!) {
                                tempImageArray.append(image)
                                print(tempImageArray)
                                // this returns a full array
                            }
                        }
                    })
            }
        }
        //self.packImage.append(tempImageArray)
        print(tempImageArray)
        //this returns []
        self.collectionView?.reloadData()
    }
  })

}

------------ 编辑-------------------- 使用 GitHub 上可用的 parseUI 中的 PFImageView

packQuery.findObjectsInBackground(block: { (objectsArray, error) in
    if error != nil {
        print(error!)
    } else if let packs = objectsArray {

        for object in packs {

            let arrayName = object.object(forKey: "packName") as! String
            let arrayDescription = object.object(forKey: "packDesctription") as! String
            let arrayTitle = object.object(forKey: "packTitle") as! String
            let arrayImage = object.object(forKey: "file") as! PFFile

            self.packArray.append(packStruct(packName: arrayName, packDescription: arrayDescription, packTitle: arrayTitle, packImage: arrayImage))
        }
        self.collectionView?.reloadData()
    }
})

Answer 1

    packQuery.findObjectsInBackground(block: { (objectsArray, error) in
        if error != nil {
            print(error!)
        } else if let packs = objectsArray {

            for object in packs {

                let arrayName = object.object(forKey: "packName") as! String
                let arrayDescription = object.object(forKey: "packDesctription") as! String
                let arrayTitle = object.object(forKey: "packTitle") as! String
                let arrayImage = object.object(forKey: "file") as! PFFile

                self.packArray.append(packStruct(packName: arrayName, packDescription: arrayDescription, packTitle: arrayTitle, packImage: arrayImage))
            }
            self.collectionView?.reloadData()
        }
    })