Question

There are cases in my app where my repositories require passing different arguments to constructors of the concrete types. I want to be able to do something like this:

var arg = (x == y) ? z : a;
ObjectFactory.GetInstance<IRepository>(arg);

Where the argument can only be constructed at the time of creating the Repository instance depending on some condition.

How can this be done?

Answer 1

As @Steven also says, I think that if possible you should let the class that needs the dependency (that has a dynamic argument) take a factory as a parameter so that you can control the creation from the consumer.

With structure map there is built in support for this so that you don’t have build a factory class.

Let the consumer take a Func as a ctor argument and create the repository (dependency) by invoking the Func with the argument:

public class Consumer
{
    public Consumer(Func<ArgumentType, IRepository> repositoryFactory)
    {
      _repositoryFactory = repositoryFactory;
    }

    public void CallRepository()
    {
       ArgumentType arg = (x == y) ? z : a;
       var repository = _repositoryFactory(arg);
       repository.GetById(...);
    }
}

In the configuration for structure map, you can configure the func:

For<Func<ArgumentType, IRepository>>().Use( arg => new Repository(arg));