creating methods for objects

[André]

Hi,

is it possible to override methods for one specific object, like you can
do in Ruby? Something like:

--8<--

class A {
public:
void method();
}

void A::method() {
// do something...
}

A x = new A();

void x::method() {
// do something else...
}

--8<--

Or anything close to that?

Thanks,

Andre'

[David Harmon]

On Fri, 18 Jun 2004 16:31:01 -0300 in comp.lang.c++, André
<an**********@s yspoint.com.br> wrote,

is it possible to override methods for one specific object, like you can
do in Ruby?

No. You might declare a derived class just for that one object.
You might use a pointer to a function, or some similar low-level
hackery.

[Phlip]

André wrote:

is it possible to override methods for one specific object, like you can
do in Ruby? Something like:

--8<--

class A {
public:
void method();
}

void A::method() {
// do something...
}

A x = new A();

void x::method() {
// do something else...
}

--8<--

Or anything close to that?

No.

C++ was invented to fit the C compiler and linker model, with minimal
changes to legacy compilers. Each translation unit must contain the same
definition of each method, just to simplify the linker's requirements.

Investigate function pointers and method pointers, to let 'x' point to a
method different from its class's method.

Why can't you just use Ruby if you need it? C++ is for big, low-level
systems; not for the average code written today.

--
Phlip
http://industrialxp.org/community/bi...UserInterfaces

[JKop]

Untested code, but you'll get the jist.
class BarnyardAnimal
{
private:

int something;

static int EatDefault(Barn yardAnimal& me, int food)
{
me.something = 7 + food; //Accessing member variable
}

public:

int (*pEat)(Barnyar dAnimal&,int);

int Eat(int food)
{
pEat(*this,food );
}

BarnyardAnimal( void) : Eat(EatDefault)
{

}

};
int main(void)
{
BarnyardAnimal cow;

cow.Eat(5); //Default function

cow.Eat = ReturnFunctionP ointer();

cow.Eat(7); //Calls other function
}
-JKop

[JKop]

JKop posted:

BarnyardAnimal( void) : Eat(EatDefault)
{

}
TYPO TYPO TYPO

BarnyardAnimal( void) : pEat(EatDefault )
{

}


int main(void)
{
BarnyardAnimal cow;

cow.Eat(5); //Default function

cow.Eat = ReturnFunctionP ointer();

TYPO TYPO TYPO

cow.pEat = ReturnFunctionP ointer();


cow.Eat(7); //Calls other function
}

-JKop

[JKop]

Ignore my last 2 posts. I'll rewrite the whole lot here without typos and
errors. The following compiles:
class BarnyardAnimal
{
private:

int something;

static int EatDefault(Barn yardAnimal& me, int food)
{
me.something = 7 + food; //Accessing member variable
}

friend int EatOther(Barnya rdAnimal&, int);

public:

int (*pEat)(Barnyar dAnimal&,int);

int Eat(int food)
{
pEat(*this,food );
}

BarnyardAnimal( void) : pEat(EatDefault )
{

}

};

int EatOther(Barnya rdAnimal& me, int food)
{
;
}

int main(void)
{
BarnyardAnimal cow;

cow.Eat(5); //Default function

cow.pEat = EatOther;

cow.Eat(7); //Calls other function
}

-JKop

[Ioannis Vranos]

Phlip wrote:

C++ is for big, low-level
systems; not for the average code written today.

What's that suppose to mean? I use C++ to build Windows (.NET)
applications elegantly and efficiently.


Regards,

Ioannis Vranos

[Ioannis Vranos]

André wrote:

Hi,

is it possible to override methods for one specific object, like you can
do in Ruby? Something like:

--8<--

class A {
public:
void method();
}

void A::method() {
// do something...
}

A x = new A();

void x::method() {
// do something else...
}

--8<--

Or anything close to that?

Thanks,

Andre'

You can use pointers to member functions, or define other "external"
functions or so something like:
class base1
{
// ...

public:
virtual void method() { ... }
// ....
};

base1 obj1;
// ...
class base2: public base1
{
public:
void method() { new definition }
};
base2 obj2;


Regards,

Ioannis Vranos

[Mike Austin]

"Ioannis Vranos" <iv*@guesswh.at .grad.com> wrote in message
news:ca******** ***@ulysses.noc .ntua.gr...

Phlip wrote:

C++ is for big, low-level
systems; not for the average code written today.

What's that suppose to mean? I use C++ to build Windows (.NET)
applications elegantly and efficiently.

Wrong. You use Managed C++ to build Windows .NET applications.

Mike Austin

[Ioannis Vranos]

Mike Austin wrote:

"Ioannis Vranos" <iv*@guesswh.at .grad.com> wrote in message
news:ca******** ***@ulysses.noc .ntua.gr...

Phlip wrote:

C++ is for big, low-level
systems; not for the average code written today.

What's that suppose to mean? I use C++ to build Windows (.NET)
application s elegantly and efficiently.

Wrong. You use Managed C++ to build Windows .NET applications.

:-) What do you mean? The so called "managed extensions" are
system-specific extensions for the specific platform. For example for
X-Windows Applications you can use the QT API. For Windows you can use
Borland's CLX/VCL.


Regards,

Ioannis Vranos