default factory spoils TDD benefits of IoC

[Glenn-Meister]

For me, one big benefit of IoC is deferring the selection of actual type that gets instantiated. Currently, the resolver has a default factory that creates an object that is an instance of the return type. This means that I cannot use virtual methods in the return type which pretty much limits my selection of type that actually gets instanced.

[Adam Young]

Doesn't have to.  The default Factory is just the simplest approach.  I'll try to put together an example that shows how you can use a derived type.  You have to register your own factory to do it:

I've checked code into the simple example on the TRUNK that shows creating an instance of type Base that is backed by the subclass Derived.

class Base {
public:
  virtual ~Base(){};
  virtual void do_action();
};

class Derived : public Base {
public:
  virtual ~Derived(){};
  virtual void do_action();
};

Create a factory method….

Base* makeBase(Zone& zone){
  return new Derived();
}

and register it:

supply<Base>::configure(makeBase);

Then use it:

Base * base = supply<Base>::fetch(request1);
base->do_action()