Question

我有一个协议ImagePickerPresentable：

protocol ImagePickerPresentable {
   var imagePicker: UIImagePickerController? { get set }
   func presentImagePicker(withSourceType: UIImagePickerControllerSourceType) throws
   func dismissImagePicker()
   weak var delegate: ImagePickerPresentableDelegate? { get set }
}

我有两个函数的默认实现扩展。

extension ImagePickerPresentable where Self: UIViewController

ImagePickerPresentableDelegate：

protocol ImagePickerPresentableDelegate: class {
    func imagePicker(imagePicker: UIImagePickerController, didFinishPickingImage image: UIImage?, withSuccess success: Bool)
}

我尝试将ImagePickerPresentable扩展为imagePicker委托函数的默认实现：

extension ImagePickerPresentable where Self: UIImagePickerControllerDelegate & UINavigationControllerDelegate {

 func imagePickerControllerDidCancel(picker: UIImagePickerController) {
    dismissImagePicker()
}

 func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
// No Callback
    if let editedImage = info[UIImagePickerControllerEditedImage] as? UIImage {
        delegate?.imagePicker(imagePicker: picker, didFinishPickingImage: editedImage, withSuccess: true)
    } else if let originalImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
        delegate?.imagePicker(imagePicker: picker, didFinishPickingImage: originalImage, withSuccess: true)
    } else {
        delegate?.imagePicker(imagePicker: picker, didFinishPickingImage: nil, withSuccess: false)
    }
  }
}

在采用协议的视图控制器中，我将self指定为imagePicker委托，但是当imagePicker完成拾取媒体时，ImagePickerPresentable不会获得回调。

如果我直接在视图控制器中实现图像选择器委托功能，我会得到回调。我可以在协议中设置一个处理图像选择器委托函数输出的函数，但是可以让图像选择器委托直接使用ImagePickerPresentable委托函数的默认实现吗？

由于我的View Controller符合ImagePickerPresentable，UIImagePickerControllerDelegate和UINavigationControllerDelegate，我认为ImagePicker委托可以识别ImagePickerPresentable扩展中的委托函数。

Answer 1

您可以使用多播委托来实现此目的。

Answer 2

这里要检查两件事。

imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])被叫到哪里？它被召唤了吗？
我要添加一个guard语句来解包delegate，然后返回另一个语句一种不成功展开的回调。

发布更多代码，例如您正在使用的示例控制器。

使用具有默认委托实现的其他协议将委托分配给类？

2 个答案: