从iOS错误的Documents文件夹内的文件夹保存并获取图像

在应用程序启动时，我正在Documents目录中创建一个文件夹（如果尚未存在）。这很棒！

我正在下载一些图像，并希望保存它们以备后用。我的问题是我的代码似乎将文件存储在文档目录中，该目录与下一次应用程序启动时的目录不同。我知道自iOS8起，文件目录可以在启动之间更改。因此，我总是在检索Documents文件夹的路径。有人可以回答我为什么此代码无法正确获取图像的路径吗？

func requestImage(let url: String,let isbn: String, numberInRow: Int){
    var documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0]
    documentsPath.appendContentsOf("/bookImages")
    print("Image folder path is: \(documentsPath)")
///var/mobile/Containers/Data/Application/E6B66A15-F166-46FE-A577-9B0D911F5C92/Documents/bookImages

    let pathComponent = isbn.stringByAppendingString(".jpg")
        print("Suggested filename: \(pathComponent)") //1234567891234.jpg

        let imagePath = documentsPath.stringByAppendingString("/\(pathComponent)")
        print("Image to be saved at: \(imagePath)")
// /var/mobile/Containers/Data/Application/E6B66A15-F166-46FE-A577-9B0D911F5C92/Documents/bookImages/9788202350420.jpg
        if (data != nil){
            NSFileManager.defaultManager().createFileAtPath(imagePath, contents: data!, attributes: ["YES" : "NSURLIsExcludedFromBackupKey"])

            self.books[numberInRow].setValue(pathComponent, forKey: "imageurl")
        }



    }

当我想显示这些图像时，我在视图控制器中有这个图像

let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0]
let imageFolderPath = documentsPath.stringByAppendingString("/bookImages")


if let image = bookData.valueForKey("imageurl") as? String
            {
                print("Imagepath: \(self.imageFolderPath)/\(image)")
// /var/mobile/Containers/Data/Application/DB1F6FE9-1071-41A6-9E87-2A3D32ECD2B9/Documents/bookImages/9788202350420.jpg
let imagePath = self.imagePath.stringByAppendingString("/\(image)")

                reuseableCell.bookCover.image = UIImage(contentsOfFile: imagePath)
            }

我删除了很多不相关的代码。为什么找不到要显示的图像？

如果有人理解错误代码，则在这里：

BOMStream BOMStreamWithFileAndSys(int, off_t, size_t, int, char *, BomSys *): read: No such file or directory

编辑：在应用程序启动时，我正在Documents / bookImages中搜索文件，并且文件在那里。

let paths: NSArray = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.AllDomainsMask, true)
    if let documentDirectory = paths.firstObject{
        do{
            var path = documentDirectory as! String
            path.appendContentsOf("/bookImages")

            let documents = try NSFileManager.defaultManager().contentsOfDirectoryAtPath(path)

            for files in documents {
                let urlForm = NSURL.fileURLWithPath((path) + "/" + files)

                do{
                    try print("\(files): \(urlForm.resourceValuesForKeys([NSURLIsExcludedFromBackupKey])), with filepath: \(urlForm)")
                    //Prints out folder and files in the desired location

                } catch let error as NSError{
                    print("Can't find key: \(error)")
                }

            }

        }catch let error as NSError{
            print("Can't retrieve contents: \(error)")
        }
    }


9788202350420.jpg: ["NSURLIsExcludedFromBackupKey": 0], with filepath:    file:///var/mobile/Containers/Data/Application/DB7BA523-6F75-42CF-92E6- ED2AF171D1AA/Documents/bookImages/9788202350420.jpg
9788203193538.jpg: ["NSURLIsExcludedFromBackupKey": 0], with filepath: file:///var/mobile/Containers/Data/Application/DB7BA523-6F75-42CF-92E6-ED2AF171D1AA/Documents/bookImages/9788203193538.jpg
9788203254703.jpg: ["NSURLIsExcludedFromBackupKey": 0], with filepath: file:///var/mobile/Containers/Data/Application/DB7BA523-6F75-42CF-92E6-ED2AF171D1AA/Documents/bookImages/9788203254703.jpg