Re: Best way to access methods of Objects and its sub-Objects
On 4/26/2013 11:47 AM, dotnetbuddha@googlemail.com wrote:
Hi All,
I was always unsure as how to deal with cases where one has to
access
methods of objects contained with in the class. Basically, if we have a
complex system as a car, where things can be abstracted in several
classes, what is the ideal way to access one/several methods of an
object contained in the class, which inturn contain additional classes ?
To explain what I mean, i wrote some pseudo code below. For example,
I
like to check the health of the car. While coding, I would normally
prefer method-1 where the task of checking is delegated to each
individual method. Where as some of my collegues argue this leads to
several methods which do nothing but delegating the task further down.
And suggest something like in method-2.
I am grateful for your time and suggestions. Thank you.
Pseudo code:
-----------
class Tyre;
??? No known interface in Tyre...
class MovingParts
{
...
...
Tyre m_Tyre;
public:
Tyre* GetTyre() { return &m_Tyre; }
void CheckTyrePressure()
Probably
void CheckTyrePressure() const
(or does checking pressure changes the state of 'MovingParts' object?)
and perhaps there is some kind of side effect since this function does
not seem to return any value, nor does it have any arguments beyond
'this'. Consider documenting that somehow.
{
m_Tyre.CheckTyrePressure();
The compiler is unlikely to accept this code without seeing the
definition of 'Tyre' type.
}
};
class Car
{
...
...
MovingParts m_movingParts;
public:
...
...
bool CheckCarHealth()
bool CheckCar
{
...
m_movingParts.CheckTyrePressure();
...
}
MovingParts* GetMovingPartsHandler()
{
return &m_MovingParts;
}
};
int main()
{
std::list<Car*> myCars;
...
...
// Check the health of all cars
for (std::list<Car*>::iterator carIdx=myCars.begin(); carIdx!=myCars.end(); ++carIdx)
In C++11 consider doing
for (Car* pCar : myCars)
{
// Method-1
carIdx->CheckCarHealth();
// Method-2
carIdx->GetMovingPartsHandler()->GetTyre()->CheckTyreProfile();
}
...
...
}
If your question is purely about the differences I see between the two
ways of invoking the interface, then my answer is to hide it. Hidden
interface is the best abstraction, the ultimate black box. The code
that uses the results does not have to know even that the interface
actually exists. The the outside observer the car can check its health
and what it entails is of no consequence. Unless they actually know
what they are looking for, in which case you probably want to design a
special "mechanic" interface who would request all those part-by-part
interfaces and interrogate those individually...
To conclude: create those interfaces that your user is going to want to
use. If you can see both uses, create both interfaces.
V
--
I do not respond to top-posted replies, please don't ask