CODEWITHSUNDEEP
c#multiple-inheritance
SinisterMJ
SinisterMJ

Reputation: 3509

Issue with inheritance in C#

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?

Upvotes: 1

Views: 107

Answers (4)

GazTheDestroyer
GazTheDestroyer

Reputation: 21241

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.

Upvotes: 2

Azodious
Azodious

Reputation: 13872

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

Can't Camera be contained in a Form?

Upvotes: 1

RustamIS
RustamIS

Reputation: 697

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

public interface MasterCamera { ... }

and it must work.

Upvotes: 2

Tigran
Tigran

Reputation: 62248

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.

Upvotes: 1

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