How to return an object that implements an interface from a method

Question

I'm trying to learn interfaces and want to try the following:

Let's say I have an interface named ICustomer that defines basic properties (UserID, UserName, etc). Now, I have multiple concrete classes like ProductA_User, ProductB_User, ProductC_User. Each one has different properties but they all implement ICustomer as they are all customers.

I want to invoke a shared method in a factory class named MemberFactory and tell it to new me up a user and I just give it a param of the enum value of which one I want. Since each concrete class is different but implements ICustomer, I should be able to return an instance that implements ICustomer. However, I'm not exactly sure how to do it in the factory class as my return type is ICustomer.

Thing to note about interfaces in .NET: They can be used as object types. So if Two random objects (Car and Telephone) both implement the interface ILike, you can have a function return either types by specifying ILike as the return type of the function. — Omar
– Omar, Commented Nov 12, 2009 at 20:51

Marcel Gosselin · Accepted Answer · 2009-11-12 20:53:01Z

7

All you have to do is create your object like this:

class ProductA_User : ICustomer
{
    //... implement ICustomer
}
class ProductB_User : ICustomer
{
    //... implement ICustomer
}
class ProductC_User : ICustomer
{
    //... implement ICustomer
}

class MemberFactory 
{
     ICustomer Create(ProductTypeEnum productType)
     {
         switch(productType)
         {
             case ProductTypeEnum.ProductA: return new ProductA_User();
             case ProductTypeEnum.ProductB: return new ProductB_User();
             case ProductTypeEnum.ProductC: return new ProductC_User();
             default: return null;
         }
     }
}

edited Nov 12, 2009 at 20:53

answered Nov 12, 2009 at 20:44

Marcel Gosselin

4,7262 gold badges36 silver badges55 bronze badges

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

Comments

kemiller2002 · Accepted Answer · 2009-11-12 20:43:04Z

1

When you call the method all you have to do is return the object as normal. It's mapping it to the interface where it comes into play.

ICustomer obj = MemberFactory.ReturnObjectWhichImplementsICustomer();

answered Nov 12, 2009 at 20:43

kemiller2002

116k28 gold badges201 silver badges255 bronze badges

Comments

qid · Accepted Answer · 2009-11-12 20:44:34Z

0

The factory method would include code that does something roughly like this:

switch (customerType)
{
case CustomerType.A:
   return new ProductA_User();
case CustomerType.B:
   return new ProductB_User();
case CustomerType.C:
   return new ProductC_User();
}

answered Nov 12, 2009 at 20:44

qid

1,91311 silver badges15 bronze badges

Collectives™ on Stack Overflow

How to return an object that implements an interface from a method

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related