组合和继承 - 抽象类

Question

Lets suppose i have a super class WorkStation , and two subclass StationNormal , StationAdvanced . I have another class Robot , which has a WorkStation pointer that will start as a StationAdvanced but it can change, but my class WorkStation is a abstract class. I think class Robot should be something like this:

class Robot{
 private: 
       WorkStation * actualStation;
...
}

My question is how Robot class constructor should be defined if my class WorkStation is abstract.

Answer 1

You need to let StationNormal and StationAdvanced inherit WorkStation An example would be:

class StationNormal:public WorkStation
{
  ....
}

public Robot(WorkStation* workStation)
{
  actualStation = workStation;
}

In main method for example:

new Robot(new StationNormal()) ;

Answer 2

I think the following should be sufficient:

class Robot{
 private: 
        WorkStation * actualStation;
 public:
        Robot();
        Robot(WorkStation * w);
}

Robot::Robot() // constructor that takes no arguments
{
    actualStation = new StationAdvanced();
}

Robot::Robot(WorkStation * w) // constructor that takes specific WorkStation
{
    actualStation = w;
}

You can invoke it with:

Robot rob1(),
      rob2(new StationAdvanced()),
      rob3(new StationNormal());

Answer 3

Well, in your constructor you would instantiate the actual WorkStation and tell the pointer ( WorkStation * actualStation ) to point to it. Put this in your constructor:

this->actualStation = new StationAdvanced(...)