Question

I have an array of different object types (about 15 different types) , they are coming from 3rd party system.
For every type I need to make different transformation.
My original thought is to make some interface with transform function and for every type make a class and run it’s own implementation.
But like this I will need to make a really big if statement that checks the object type and make the mapping.

I am trying to learn something new here, so my question is there other ways to deal with this situation?

Answer 1

Have you considered the possibility of using a Visitor?

If you combine the visitor pattern with the use of dynamic, you could get a pretty simple implementation without any if or switch statements, or having to manually create a Type Dictionary with delegates, or similar alternatives.

Using dynamic you can avoid implementing the “accept” part of the design pattern, which I assume is useful to you since these are external types you have no control over.

Meaning, you create something like this:

public interface IVisitor
    {
        void Visit(OneType element);
        void Visit(AnotherType element);
        ....
    }

You implement that visitor, and can later call the implementation using:

visitor.Visit((dynamic)objectToTransform);

You would probably have to handle for exceptions regarding not having an appropriate overload for the Type.

That would solve the part of the problem related to executing a separate method for each type.
Now, depending on what you specifically need to do with each one, if you need automatic property mapping then AutoMapper could be very useful.