A Better Example

• I have made some changes in the newest edition Step3.
  • 
  • The BuildingT
    • Stores a reference to a warehouse.
      • We don't want to destroy the warehouse before the buildings go out of scope.
      • But they will not need the warehouse to be passed to them.
      • Initialization requires attention to detail.
        • Make sure that the warehouse is passed by reference to all instances of the constructors all the way up the line.
        • Make sure that the parent constructor is called in the ctor-initalizer.
    • I moved the warehouse to the protected area to allow all derived classes to have access to it.
    • I removed CanProduce and Produce
      • These are not common to all buidling types.
    • I made WorkersNeeded pure virtual.
      • This requires that all buildings that can be built have a WorkersNeeded function.
      • But I don't know how they will be implmeneted.
    • I added a non-vitrual Type
      • This should probably be virtual, but at this point I don't expect anyone to override it.
  • I added two more abstract classes.
    • Looking at the rules, there are two types of buldings
      • Production buildings remove goods from the warehouse and produce other goods.
      • Bonus buildings add a bonus to the sector's natural resource production.
    • So I made a class for each.
    • In Production Buildings
      • There is only a header file.
      • Produce and CanProduce are pure virtual
        • Again providing an intefrace but no implementation.
    • BonusBuildingT
      • Actually implments the *Bonus functions.
        • Each returns a 0
        • But that way I don't need to implement them unless needed in the future.
  • I added a FarmT and a SawmillT as concrete classes.
• The driver has changed quite a bit.
  • Everything (well nearly) is done with unique_ptr
    • There is one side trip where I do a cast.
    • I access the underlying raw pointer.
    • But this is only for function calls
    • Do not delet the temp pointer.
  • MakeBuilding is a primitive step to a new design pattern.
    • In this case, you might call it a factory function.
    • There are two design patterns that encapsulate this.
      • The Concrete Factory (or just factory_
      • The Abstract Factory
    • But for now we will not worry about these.
      • They are ideal for this situation.
  • Note
    • The creation of the second sawmill.
    • Store in a tmp pointer
    • Note the use of
      • The vector function back.
      • The move operator to move a unique_pointer