Switch statements are bad? [closed]

Answer 1

A switch is like any other control structure. There are places where it's the best/cleanest solution, and many more places where it's completely inappropriate. It's just abused way more than other control structures.

In OO design, it's generally considered preferable in a situation like yours to use different message types/classes that inherit from a common message class, then use overloaded methods to "automatically" differentiate between the different types.

In a case like yours, you could use an enumeration that maps to your action codes, then attach an attribute to each enumerated value that will let you use generics or type-building to build different Action sub-class objects so that the overloading method will work.

But that's a real pain.

Evaluate whether there's a design option such as the enumeration that is feasible in your solution. If not, just use the switch.

Answer 2

Use commands. Wrap the action in an object and let polymorphism do the switch for you. In C++ (shared_ptr is simply a pointer, or a reference in Java terms. It allows for dynamic dispatch):

void GameServer::perform_action(shared_ptr<Action> op) {
    op->execute();
}

Clients pick an action to perform, and once they do they send that action itself to the server so the server doesn't need to do any parsing:

void BlueClient::play() {
    shared_ptr<Action> a;
    if( should_move() ) a = new Move(this, NORTHWEST);
    else if( should_attack() ) a = new Attack(this, EAST);
    else a = Wait(this);
    server.perform_action(a);
}