Design and Architecture

Nagy Vilmos wrote:

If the rocket must have a booster, then I agree it must be a part of the
constructor to ensure its presence.

public class Rocket
{
  public Rocket()
  {
  }

  public void PreLaunchTests()
  {
    OnPreLaunchTests();
  }

  public void Launch()
  {
  }

  protected virtual void OnPreLaunchTests()
  {
  }

  protected virtual void OnLaunch()
  {
  }
}

public class SingleBoosterRocket : Rocket
{
  public List<IBooster> Boosters { get; private set; }

  public SingleBoosterRocket()
  {
    Boosters = new List<IBooster>();
  }

  public void AddBooster(IBooster booster)
  {
    Boosters.Add(booster);
  }

  protected override void OnPreLaunchTests()
  {
    // Do some pre launch tests.
  }

  protected override void OnLaunch()
  {
    if (Boosters.Count == 0)
      throw new NotEnoughBoostersException();
    // Do some other work.
  }
}

public class DualBoosterRocket : SingleBoosterRocket
{

  public DualBoosterRocket() : base()
  {
  }

  protected override void OnPreLaunchTests()
  {
    // Do some pre launch tests.
  }

  protected override void OnLaunch()
  {
    if (Boosters.Count < 2)
      throw new NotEnoughBoostersException();
    // Do some other work.
  }
}

Pete O'Hanlon wrote:

Funnily enough, that was the gist of the answer that I've just added above.

Pete O'Hanlon wrote:

We internally have a DI engine that is only 60 lines or so of code

VuNic wrote:

The Boosters.GetBooster() can be applied for both the scenarios?

+----+--------+-------+
| id | name   | price |
+----+--------+-------+
|  1 | wheel  | $1.23 |
+----+--------+-------+
|  2 | wire   | $1.50 |
+----+--------+-------+

wheels table

+----+--------+--------+
| id | cog_id | radius |
+----+--------+--------+
|  1 |    1   |   50"  |
+----+--------+--------+

wires table

+----+--------+--------+
| id | cog_id | length |
+----+--------+--------+
|  1 |    2   |   12"  |
+----+--------+--------+

Leslie Sanford wrote:

I'm not sure if this is a common approach.

Leslie Sanford wrote:

I know the joins will cost more processing, but at least the schema makes sense to me.

Bastard Programmer from Hell

Leslie Sanford wrote:

(they have sufficiently different characteristics

wan.rui@qq.com wrote:

so which way will the best way we should order ?

class CVehicle
{
public:
  virtual void Move();
}

class CCar: public CVehicle
{
public:
  void Move()
  {
    cout << "I am a car. I can be driven" << endl;
  }
}
class CBike: public CVehicle
{
public:
  void Move()
  {
    cout << "I am a bike. I can be ridden" << endl;
  }
}

class CAeroplane: public CVehicle
{
public:
  void Move()
  {
    cout << "I am an aeroplane. I can be flown" << endl;
  }
}