创建具有基类的接口，而派生类包含其自己的实现

Question

This is my code

class InternalDevice1
{
}

class InternalDevice2
{
}

class SpecificDevice1 : InternalDevice1
{
}

class SpecificDevice2 : InternalDevice2
{
}

class SpecificDevice3 : InternalDevice1
{
}

class SpecificDevice4 : InternalDevice2
{
}

class MyWholeDevice1 : IDevice
{
   MyWholeDevice(SpecificDevice1 device1, SpecificDevice2 device2) { }
   SpecificDevice1 Device { get; }   
}

class MyWholeDevice2 : IDevice
{
   MyWholeDevice(SpecificDevice3 device1, SpecificDevice4 device2) { }
   SpecificDevice3 Device { get; }  
}


interface IDevice
{
   InternalDevice1 Device { get; }
}

The problem is that the return type in IDevice is InternalDevice1 (which is more general) while I need the SpecificDevice (which is still dervied from InternalDevice) I'm encountering a problem when trying to use this:

IDevice = new MyWholeDevice ...

Answer 1

You should make your IDevice generic

interface IDevice<TDevice>
   where TDevice : InternalDevice1
{
   TDevice Device { get; }
}

Then your classes will look like this:

class MyWholeDevice1 : IDevice<SpecificDevice1>
{
   MyWholeDevice(SpecificDevice1 device1, SpecificDevice2 device2) { }
   SpecificDevice1 Device { get; }   
}

class MyWholeDevice2 : IDevice<SpecificDevice3>
{
   MyWholeDevice(SpecificDevice3 device1, SpecificDevice4 device2) { }
   SpecificDevice3 Device { get; }  
}