Issue with inheritance in C#

Question

I've got an issue with the non-allowed multiple inheritance in C#

Following scenario:

class MasterCamera { ... }

class CameraFromManufacturerA : MasterCamera { ... }

class CameraFromManufacturerB : MasterCamera { ... }

class CameraFromManufacturerC : MasterCamera { ... }

MasterCamera provides some functionality like StartCamera(), ConnectCamera(), etc. In my main code I use an object MasterCamera mCamera = CameraSelector.GetCamera(); with CameraSelector checking whether a camera from A, B or C is connected, and returns that object (e.g. CameraFromManufacturerA)

This works perfectly fine in theory, but one of these camera's API needs to use the WindowsMessageCallback (WndProc), thus I need to include for that camera only Windows.System.Forms.Form

Since C# does not allow multiple inheritance, and afaik Form has no interface class, I have to make MasterCamera inherit from Windows.System.Forms.Form

I do not want that, so how can I go around that?

RustamIS · Accepted Answer · 2012-09-12 09:10:40Z

2

You shouldn't use MasterCamera { ... } as a Class but use it as Interface like:

public interface MasterCamera { ... }

and it must work.

answered Sep 12, 2012 at 9:10

RustamIS

6978 silver badges24 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

SinisterMJ Over a year ago

Thanks, that worked. Didn't know you can use an interface as an object to call functions from.

GazTheDestroyer Over a year ago

This provides no means for implementing the common functionality.

SinisterMJ Over a year ago

That is true, but since every camera's manufacturers API is completely different, there is close to no common code at all.

GazTheDestroyer · Accepted Answer · 2012-09-12 09:12:10Z

2

This is a common problem with inheritance, which is why the GoF state "Favour composition over inheritance"

You could use the Strategy pattern. Instead of deriving different types of MasterCamera, instead derive different types of ICameraFunctionality, and store an object of that instance in your MasterCamera (or rather just Camera) class.

That way MasterCamera just does the common work, but calls its ICameraFunctionality instance to perform specific work.

answered Sep 12, 2012 at 9:12

GazTheDestroyer

21.3k10 gold badges76 silver badges109 bronze badges

Comments

Tigran · Accepted Answer · 2012-09-12 09:08:24Z

1

What if you simply invert dependency in your code. Create a Form class that overrides WindowsMessageCallback and is able to host MasterCamera object, which would be that child Camera class that you need.

answered Sep 12, 2012 at 9:08

Tigran

62.3k8 gold badges90 silver badges124 bronze badges

Comments

Azodious · Accepted Answer · 2012-09-12 09:10:54Z

1

You are trying Inheritance. Give a try to Composition also.

Can't Camera be contained in a Form?

answered Sep 12, 2012 at 9:10

Azodious

13.9k1 gold badge41 silver badges75 bronze badges

Collectives™ on Stack Overflow

Issue with inheritance in C#

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related