Question

I am using windsor castle as my IoC container, and has run in to a bit of a problem. This is best explained in code, so I´ll give it a try. I have a factory class, that should provide me with implementations of a certain interface:

public interface IObjectCreatorFactory {     IObjectCreator GetObjectCreator(Type objectType); } public interface IObjectCreator {     T CreateObject<T>(IDataRow data);     bool SupportsType(Type type); } 

Implementation of the factory class could look like this, though I am not sure this is the way to go: public interface ObjectCreatorFactory:IObjectCreatorFactory { IEnumerable specificCreators; IObjectCreator defaultCreator;

    public ObjectCreatorFactory(IEnumerable<IObjectCreator> specificCreators, IObjectCreator defaultCreator)     {         this.specificCreators= specificCreators;         this.defaultCreator= defaultCreator;     }     public IObjectCreator GetObjectCreator(Type objectType)     {         foreach (IObjectCreator creator in specificCreators)         {             if (creator.SupportsType(objectType))             {                 return creator;             }         }         return defaultCreator;     } } 

Now this would work out ok, but if I want my IObjectCreator instance to create child objects using a specific IObjectCreator, i would like to call ObjectCreatorFactory, and this obviously results in a circular reference:

public void SpecificObjectCreator:IObjectCreator {     IObjectCreatorFactory objCreatorFactory;     public SpecificObjectCreator(IObjectCreatorFactory objCreatorFactory)     {         this.objCreatorFactory = objCreatorFactory;     }     T CreateObject<T>(IDataRow data)     {         T obj = new T;         ChildObject childObject = objCreatorFactory.GetObjectCreator(typeof(ChildObject)).CreateObject<ChildObject>(data);          .......     }     bool SupportsType(Type type);         } 

This does not work out. What would be the way to go for this scenario, where the created objects are refering back to the factory for child object creators?

Answer 1

I would simply move the factory out of the constructors of the various specific object creators, and introduce a method on the IObjectCreator interface instead, responsible for initialising the creators:

public interface IObjectCreator {     T CreateObject<T>(IDataRow data);     bool SupportsType(Type type);     void Initialize(IObjectCreatorFactory factory); } 

And then just invoke Initialze(this) on each object creator passed into the factory.

In the past I’ve used custom life cycle stages to take care of automatically invoking ‘post-construction’ setup of components to both avoid circular dependencies and also to take care of other associated concerns (i.e. applying additional component configuration from an external source like a database) – but it’s probably overkill for what you need.