imagePickerController didFinishPickingMediaWithInfo未被调用

Question

我第一次尝试使用外部库WDImagePicker。下面是与我的问题相关的WDImagePicker代码。

@objc public protocol WDImagePickerDelegate {
    @objc optional func imagePicker(imagePicker: WDImagePicker, pickedImage: UIImage)
    @objc optional func imagePickerDidCancel(imagePicker: WDImagePicker)
}

@objc public class WDImagePicker: NSObject, UIImagePickerControllerDelegate, UINavigationControllerDelegate, WDImageCropControllerDelegate {
    public var delegate: WDImagePickerDelegate?

    private var _imagePickerController: UIImagePickerController!

    public var imagePickerController: UIImagePickerController {
        return _imagePickerController
    }

    override public init() {
        super.init()
        self.cropSize = CGSize(width: 320, height: 320)
        _imagePickerController = UIImagePickerController()
        _imagePickerController.delegate = self
        _imagePickerController.sourceType = .photoLibrary
    }

    public func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
        print("this line never runs\n\n")
    }
}

在我自己写的控制器中，我有这个方法，它提供了cropImagePicker的imagePickerContoller;但即使此控制器的委托是cropImagePicker，cropImagePicker的ImagePickerControllerDelegate方法永远不会被调用（我测试了所有这些）。

@IBAction func cameraButtonPressed() {
    let cropImagePicker = WDImagePicker()
    cropImagePicker.cropSize = CGSize(width: 50, height: 50)
    cropImagePicker.delegate = self
    cropImagePicker.resizableCropArea = false
    cropImagePicker.imagePickerController.delegate = cropImagePicker
    self.present(cropImagePicker.imagePickerController, animated: true, completion: nil)
}

为什么会这样？可能是因为我必须对图书馆进行迅速的3次更改吗？最重要的是，我该如何解决这个问题呢？所有的意见都表示赞赏。