A Car case

[Tim]

Dear All,

For the car case I posted before (car has some parts, and parts must
have the same maker, such as Ford), what I really concerned is that:

There are two implementations:

1.

class Car
{
public:
SetEngine(Engine*);
SetTransmission(Transmission*)
private:
Engine *m_engine;
Transmission *m_transmission;
...
};

For a Ford car

Car fordCar;
FordEngine * pFordEngine;
FordTranismission *pFordTransmission;
fordCar.SetEngine(pFordEngine);
fordCar.SetTransmission(pFordTransmission);
2.

class Car
{
public:
virtual SetEngine(Engine*);
virtual SetTransmission(Transmission*)
};

class FordCar : public Car
{
public:
virtual SetEngine(Engine*) {...}
virtual SetTransmission(Transmission*) {...}
private:
FordEngine *m_engine;
FordTransmission *m_transmission;
};

The difference is that I put the private part members is the derived
classes. I want to know which design is better and why?

I appreciate your kind help

Tim

[hbrt]

Hi, Tim!
I would rather do this in following way:
1. class Car should have two virtual public (as in your 2. solution)
2. class Car should have two handlers for Engine and Transmission -
but in PROTECTED section
3. class FordCar, derived from Car, should have overloaded functions
from its ancestor
Pros of this solution:
- you cannot create just a 'car' - it has to be FordCar, OpelCar,
FiatCar etc.
- protected section allows you to use both handlers in derived classes
- if you ever try to create a class hierarchy for Engine or/and
Transmission - you can still use your car-hierarchy: every Car has its
own engine, fully defined in derived classes.
Waiting for comments from other members :-)

hbrt

[Tim]

On Aug 21, 1:24 pm, hbrt <[e-mail]:

Hi, Tim!
I would rather do this in following way:
1. class Car should have two virtual public (as in your 2. solution)
2. class Car should have two handlers for Engine and Transmission -
but in PROTECTED section
3. class FordCar, derived from Car, should have overloaded functions
from its ancestor
Pros of this solution:
- you cannot create just a 'car' - it has to be FordCar, OpelCar,
FiatCar etc.
- protected section allows you to use both handlers in derived classes
- if you ever try to create a class hierarchy for Engine or/and
Transmission - you can still use your car-hierarchy: every Car has its
own engine, fully defined in derived classes.
Waiting for comments from other members :-)

hbrt

I have some questions on your implementation:
1. FordCar has to implement the virtual set.. functioins? Is it
repeating code?
2. In set engine to Ford, you need to check the engine type?
3. I am very interested you talking about the engine/transmission
hierarchy, considering these, it there any better design for the whole
system?
Thanks.

[Ron Natalie]

Tim wrote:

Dear All,

For the car case I posted before (car has some parts, and parts must
have the same maker, such as Ford), what I really concerned is that:

Second poster with the same question. School must be back in
session. Kiddies do your own homework.