Castle Windsor: How to prevent circular references in factory-created objects were the created objects refers back to the factory

问题

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?

回答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.

来源：https://stackoverflow.com/questions/487786/castle-windsor-how-to-prevent-circular-references-in-factory-created-objects-we

标签

dependency-injection

inversion-of-control

castle-windsor

factory