ios - 在 Parse 和 Swift 中使用本地数据存储

Question

我有一个 UIImagePickerController，它允许用户将图像添加到 localDatastore:

func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
    let pickedImage = info[UIImagePickerControllerOriginalImage] as! UIImage
    print("photo picked!") 
    //self.collectionView?.reloadData()
    //try writing to parse local datastore?

    let imageObject = PFObject(className: "imagePicked")        
    imageObject["theImg"] = PFFile(data: UIImageJPEGRepresentation(pickedImage, 0.1)!)
    imageObject["id"] = "123321"
    imageObject.pinInBackgroundWithName("imgs") { (success, error) -> Void in
        if error == nil{
            print("Object pinned!")         
            self.collectionView?.reloadData()
        } else {
            print(error)
        }
    }

    self.dismissViewControllerAnimated(true) { () -> Void in
        self.collectionView?.reloadData()
    }
}

然后在 viewDidLoad 中，我将 localDatastore 中的所有对象附加到一个数组中 -

let query = PFQuery(className: "imagePicked")
    query.fromLocalDatastore()
    query.fromPinWithName("imgs")
    // Put all of the objects found in an array
    query.findObjectsInBackgroundWithBlock { (objects, error) -> Void in
        if error == nil {              
            let objects = objects as! AnyObject
            for object in objects as! [AnyObject] {
                let pictureData = object["theImg"] as! PFFile
                pictureData.getDataInBackgroundWithBlock({ (imageData, error) -> Void in
                    if error == nil {           
                        if let imageData = UIImage(data: imageData!) where error == nil {
                            self.theImages.append(imageData)             
                            self.collectionView?.reloadData()
                            print("The images were added!")
                        }
                    } else {
                        print(error)
                    }
                }) 
            }
        } else {
            print(error)
        }
    }
}

最后，在 UICollectionView 的数据源方法中，我用来自 Parse 的图像数组填充UICollectionViewCell`。

 override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell = self.collectionView?.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) as! theCell
    //add the images from the array
    cell.theImage.image = theImages[indexPath.row]
    return cell
}

问题是我收到这个错误:

2015-09-19 15:49:35.216 SecureSearchv3[17816:700076] [Error]: Caught "NSInvalidArgumentException" with reason "*** -[_NSPlaceholderData initWithContentsOfFile:options:error:]: nil file argument":

Answer 1

我发现了同样的问题。有一种解决方法(我知道这是一篇旧文章...)

LocalDataStore 不会存储 PFiles，而 PFiles 是 UIImage 的存储方式。要绕过它，您需要将图像存储在文档目录中:

swift 3

let imageData = UIImagePNGRepresentation(image)!  
let docDir = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)  
let imageURL = docDir.appendingPathComponent("tmp.png")  
try! imageData.write(to: imageURL)  

然后检索:

let newImage = UIImage(contentsOfFile: imageURL.path)!

这不处理任何错误......

使用您的 PFObject，您可以将其保存在本地数据存储区“tmp.png”或您称之为的任何路径中，以便轻松调用。