从Parse下载的图像不会显示为UIImageView

Question

有问题的代码是

    if let productImageFile = productData!["productImage"] as? PFFile {
                    productImageFile.getDataInBackgroundWithBlock {
                        (imageData: NSData?, error: NSError?) -> Void in
                        if error == nil {
                            if let imageData = imageData {
                                let image = UIImage(data:imageData)
                                    self.productImageView.image = image
                            }
                        }
                    }
                }

我没有任何错误，但图像只是不想从Parse加载。其他所有东西都加载并显示得很好，但无论我等待多久，图像都不会加载。如果我将UIImageView更改为PFImageView，并在接口生成器中将UIImageView的类更改为PFImageView，则会给出3个链接器错误：

架构x86_64的未定义符号：“_ kPFErrorInvalidImageData”，引用自：___ 32- [PFImageView loadInBackground：] _ block_invoke30在ParseUI中（PFImageView.o） “_kPFErrorUnsavedFile”，引自： - ParseUI中的[PFImageView loadInBackground：]（PFImageView.o）

ld：找不到架构x86_64的符号

clang：错误：链接器命令失败，退出代码为1（使用-v查看调用）

感谢任何帮助。完整的ViewController代码如下。

    import UIKit
    import Parse
    import Bolts
    import ParseUI

    class ViewController: UIViewController {
@IBOutlet weak var dayOfTheWeekLabel: UILabel!
@IBOutlet weak var productTitleLabel: UILabel!
@IBOutlet weak var productImageView: UIImageView!
@IBOutlet weak var productPriceLabel: UILabel!
@IBOutlet weak var productDescriptionLabel: UILabel!
@IBOutlet weak var buyButton: UIButton!
@IBOutlet weak var refreshButton: UIBarButtonItem!

override func viewDidLoad() {
    super.viewDidLoad()

    //Create new PFQuery to retrieve info from Parse
    var query: PFQuery = PFQuery(className: "MyProduct")

    //function to get the data
    func getProductData (){
        //call function to get the data from parse by specifyng an objectId
        query.getObjectInBackgroundWithId("XXXXXXXXXX") {
            (productData:PFObject?, error:NSError?) -> Void in
            if error == nil && productData != nil {
                //Extract values from the productData PFObject and store them in constants
                let dayOfTheWeek = productData!.objectForKey("day") as! String
                let productTitle = productData!.objectForKey("productTitle") as! String
                //-----start image loading
                if let productImageFile = productData!["productImage"] as? PFFile {
                    productImageFile.getDataInBackgroundWithBlock {
                        (imageData: NSData?, error: NSError?) -> Void in
                        if error == nil {
                            if let imageData = imageData {
                                let image = UIImage(data:imageData)
                                    self.productImageView.image = image
                            }
                        }
                    }
                }

                //-----end image loading
                let productPrice = productData!.objectForKey("productPrice") as! String
                let productDescription = productData!.objectForKey("productDescription") as! String

                //take the saved constants and assign their values to the labels and UIImage on screen
                self.productTitleLabel.text = productTitle
                self.dayOfTheWeekLabel.text = dayOfTheWeek
                //self.productImageView.image! = productImageFile
                self.productPriceLabel.text = productPrice
                self.productDescriptionLabel.text = productDescription

            } else if error != nil {
                println("Could not load data from Parse")
            }



        }

    }


    //Print out a message if we're able to get to this part of the program.
    println("Reached getProductData function. Now asking for data.")
            getProductData()

}