I am trying to do something like this with c++.
void showContensofArray(void *data[])
{
//In this function have to display the values of respective objects.
// Any ideas how do I do it?
}
int main(){
A phew(xxx,abcdefg); //object of class A
B ball(90),ball2(88); //object of class B
void *dataArray[2];
dataArray[0] = &ph1;
dataArray[1] = &ball;
showContentsofArray(dataArray); //function
}
If you want to treat the objects in the data[] generically (i.e by calling a common function on them to extract a description or values) then define a class hirachy for your objects and in your showContentsofArray function call virtual methods on your (common base class) object pointers.
This is a textbook example of Polymorphism:
"polymorphism allows values of different data types to be handled using a uniform interface."
In the example below the base class BaseObject defines the uniform interface.
class BaseObject {
virtual string description() { return "Base object"; }
virtual bool bounces() { return false; }
}
class B : public BaseObject {
string description() { return "Im a B object" }
bool bounces() { return true; }
}
class A : public BaseObject {
string description() { return "Im an A object" }
}
void showContensofArray(BaseObject* data[], int size) {
for (int i=0; i<size; i++) {
cout << data[i]->description();
if (data[i]->bounces())
cout << "I bounce!";
}
}
int main() {
A phew(xxx,abcdefg); //object of class A
B ball(90),ball2(88); //object of class B
BaseObject* dataArray[2];
dataArray[0] = &ph1;
dataArray[1] = &ball;
showContentsofArray(dataArray);
}
Will output:
Im an A object
Im a B object
I bounce!
void showContensofArray(void *data[], int len)
{
int i;
for(i=0;i<len;i++){
((Base*)(data[i]))->print();
}
}
And every Class should have an implementation of the method print() that knows how to print its values.
You could also use inheritance.
EDIT:
@Ricibob's answer is correct, but if you need to do the casting inside the function, you need to do something like this:
#include <iostream>
using namespace std;
class Base{
public:
virtual void print()=0;
};
class A: public Base{
public:
void print(){
cout<<"Object A"<<endl;
}
};
class B: public Base{
public:
void print(){
cout<<"Object B"<<endl;
}
};
void showContensofArray(void* data[], int len)
{
int i;
for(i=0;i<len;i++){
((Base*)(data[i]))->print();
}
}
int main(){
A a;
B b;
void* v[2];
v[0]= &a;
v[1] = &b;
showContensofArray(v,2);
return 0;
}
You can't evade inheritance.
Just cast back to the original type:
A* p1 = static_cast<A*>(data[0]);
B* p2 = static_cast<B*>(data[1]);
