In my current project, I find my self making factories, but for two very distinct reasons:
Reason #1: To assist my IoC container if a particular class needs an parameter that is only known when the class is created. This might also include reading data from a config. This kind of factory contains no business logic, only initialization logic.
Reason #2: The creation of an entity needs complex validation logic, and I want to keep this logic out of my constructor so it stays simple. This kind of factory is only about business logic around the creation of a new entity.
Furthermore, when I create a factory for reason #2, I find myself tempted to put deletion logic there as well, as the deletion of the entity is often complex and beyond the scope of the entity being deleted; however, one would be hard pressed to call a class with a deletion method a factory.
Reason #1 Example:
class WidgetRepositoryFactory
{
IUserRepository Create(userType)
{
int configValue = int.Parse(Config.get("ConfigValue"));
IUserRepository repo = userType == "user1" : new User1Repo(configValue) : new User2Repo(configValue);
return repo;
}
}
Reason #2 Example:
class WidgetFactory
{
Result<Widget> Create(var1, var2)
{
Result r = new Result();
if (var1 < 0)
{
r.AddError("var1 too low!");
return r;
}
if (var1 > var2)
{
r.AddError("var1 too high!");
return r;
}
r.Obj = new Widget(var1, var2);
r.Success = true;
return r;
}
}
When I create a factory for reason #2, is it really correct to call it a factory? Is there a better term for this kind of class? Is there preexisting terminology to describe these two very distinct cases?