具有泛型的C＃工厂模式

Question

I want to do a factory class for myInterface , however I can't call a constructor for a concrete class because the factory class is obliged to a specific parameter T .

Is there a way to make a factory class for a generic interface?

Simplified Example

interface myInterface<T>
{
    void work(T input);
    T getSomething();
}

class A : myInterface<int>
{
    //implementation
}

class B : myInterface<someClass>
{
   //implementation
}

interface Factory<R,T>
{
     R Create(T type);
}
class myFactory<T> : Factory<myInterface<T>, string>
{
     myInterface<T> Create(string type) {
          if(type == "A")
               //return new A object
          if(type == "B")
               //return new B object
          //some default behavior
     }
}

Answer 1

The Factory Pattern is generic by default, since the whole purpose of such pattern is to return objects of different types, depending on the value you provide to your method.

There shouldn't be much of a code within the factory other than whatever you need in order to initialize an object of the desired type.

In the code you've provided you're expecting to return an object of myInterface type, however it is not quite possible since you'll have to specify different return types which will be chosen by the value of your type parameter. You're losing the whole point of the Factory Pattern since you're already declaring a factory of a specific type - means you'll be creating objects only of that type (concept is lost).

What I would have done is creating another class that will serve as a layer for both classes A and B (both classes will have to inherit from it). Then I would declare the return type of your factory to the type of that class.

Keep in mind that each class implements the same generic interface but of different type.

Here's a brief example:

    interface myInterface<T>
    {

    }
    class LayerClass
    {

    }
    class A : LayerClass, myInterface<int>
    {
        //implementation
    }

    class B : LayerClass, myInterface<object>
    {
       //implementation
    }

    public static void Main(string[] args)
    {

    }
    class myFactory<T>
    {
        LayerClass Create(string type) 
        {
            if(type == "A")
                return (LayerClass)new A();
            if(type == "B")
                return (LayerClass)new B();
            return null;
         }
    }