Question

class OSwitch {
private:
    Operator *operators[];
    //int variable; <-- unused variable

public:
    OSwitch() {}
    ~OSwitch() {}

void setOperator(int id, Operator *op) {
    operators[id] = op;
}

void execute(int id) {
    operators[id]->execute();
}

};

There are several subclasses of the abstract baseclass Operator.
When calling setOperator() for more than one time, the array “forgets” the last element.

for example

XOperator a;
YOperator b;
os.setOperator(1,a);
os.setOperator(2,b);
os.execute(1); // <- wont work

But when the int variable (or any other variable in OperatorSwitch) is declared, it works.
I dont have any idea how this works.

Thanks for any hint.

Answer 1

Your member variable operators is an unsized array, which is an incomplete type and not allowed in a class definition.

What you probably want instead is a map of integers to pointers:

#include <map>

class OSwitch
{
private:
    std::map<int, Operator *> operators;
public:
    void setOperator(int id, Operator *op) { operators[id] = op; }
    void execute(int id) { operators[id]->execute(); }
};

Note that it will be an error to call execute on an ID that has not been assigned a valid pointer. You can make this more robust by checking for existence of the map element first.