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Marlene Miller · Guest

Hello.

I want to allow variations of a class, so that my event objects can use
different algorithms to select the next server. I am new to OO. I've read
about various ways to do things. They all work. But I don't know how to
choose.

Question: Would you please offer some guidelines or insights or reasons on
how you would choose?

1. Create a derived class and override the select function.

class E1 {
public:
void f() { S* s = select(); ... }
protected:
virtual S* select();
};

class B : public E1 {
S* select();
};

2. The strategy pattern - a family of algorithms with a common interface.

class C { //strategy interface
public:
virtual S* select();
};

class D : public C { //a special algorithm
public:
S* select();
};

class E2 {
C* c;
public:
E2(C* cc) : c(cc) {}
void f() { S* s = c->select(); ... }
};

3. The strategy pattern using function objects.

class SelectS {
public:
virtual S* operator()();
};

class FixedS : public SelectS {
public:
S* operator()();
};

class E3 {
SelectS* ss;
public:
E3(SelectS* p) : ss(p) {}
void f() { S* s = (*ss)(); ... }
};

Thank you. - Marlene

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