Inheritance from generic interfaces

c#, generics, inheritance, interface

Solution

Not sure if this is a typo, but should this:

interface ISpecialFactory<T>
        where T : ICloneable, IFactory<T>

have really been

interface ISpecialFactory<T> : IFactory<T>
        where T : ICloneable

Really, I think this is probably what you're trying to do:

public class Computer : ICloneable
{ 
    public object Clone(){ return new Computer(); }
}

public interface IFactory<T>
{
    T Get();    
}

public interface IComputerFactory : IFactory<Computer>
{
    Computer Get();
}

public interface ISpecialFactory<T>: IFactory<T>
    where T : ICloneable
{
    T Get();
}

public class MyFactory : IComputerFactory, ISpecialFactory<Computer>
{
    public Computer Get()
    {
        return new Computer();
    }
}

Live example: http://rextester.com/ENLPO67010

Problem

I don't know how to solve a problem with generic interfaces. Generic interface represents factory for objects: ``` interface IFactory<T> { // get created object T Get(); } ``` Interface represents factory for computers (Computer class) specyfing general factory: ``` interface IComputerFactory<T> : IFactory<T> where T : Computer { // get created computer new Computer Get(); } ``` Generic interface represents special factory for objects, which are cloneable (implements interface System.ICloneable): ``` interface ISpecialFactory<T> where T : ICloneable, IFactory<T> { // get created object T Get(); } ``` Class represents factory for computers (Computer class) and cloneable objects: ``` class MyFactory<T> : IComputerFactory<Computer>, ISpecialFactory<T> { } ``` I get compiler error messages In MyFactory class: ``` The type 'T' cannot be used as type parameter 'T' in the generic type or method 'exer.ISpecialFactory<T>'. There is no boxing conversion or type parameter conversion from 'T' to 'exer.IFactory<T>'. The type 'T' cannot be used as type parameter 'T' in the generic type or method 'exer.ISpecialFactory<T>'. There is no boxing conversion or type parameter conversion from 'T' to 'System.ICloneable'. ```

Original source