Using Dependency Injection to Decide Which Implemention to Create at Runtime

Question

I am writing a desktop GIS application and it supports MapXtreme, MS Virtual Earth and our Custom Map Engine.Users of application can change the map engine at run-time by selecting from dropdownlist.I have a Factory class to change map engine like this.

public class MapFactory implements IMapFactory
{
    public IMapEngine createInstance(MapType type)
    {
       if(type==MapType.MapXtreme)
          return new MapXtremeEngine();
       else if(type==MapType.VirtualEarth)
          return new VirtualEarth();
       //....other code
    }
}

Can I use a Dependency Injection Framework to create suitable MapEngine implementation at run-time by type parameter?

Answer 1

Your example is the exact right pattern for conditionally instantiating an object. Anywhere you need to create an instance, accept IMapFactory in the constructor.

The most a DI framework should do is hand out the IMapFactory instance.