CODEWITHSUNDEEP
c++inheritancecastingtypeid
optional
optional

Reputation: 283

C++ casting and typeid

I got a function that have two base class pointers and depending on the subclass, other functions should be called...

Like this:

    void function(A* a, A* a2){

    if (typeid(*a).name() == "B"){
        if(typeid(*a2).name() == "C"){
            otherFunction(); 
        }
        if(typeid(*a2).name() == "D"){
            otherFunction2(); 
        }
    }
  }

However, there's a whole buncha problems:

1) I've read that typeid.name yield different result depending on the compiler and therefore I don't want to use it.

2) I've considered creating an instance of "B" and instead writing if(typeid(*a2) == typeid(instanceOfB)) but that would be a lot of work since there are plenty of constructor arguments...

3) I've also considered using dynamic_cast but some subclasses look like this: 

  A <-- B <-- C

so if if I wanted to check if the argument is B with dynamic cast, it would pass even if the argument is in fact C because C inherits from B

Edit: It seems I'll have to reconsider the design but since many have stated the design is flawed I'll quickly explain what my train of thought:

There's a window. Several different objects are located inside the window and move around, a game. This function was supposed to function as a collision detection. Like this: Go through all objects on the screen, check if the have collided. Take the two collided objects as arguments and call this function. This function looks up a buncha different collisions like "if a is "an arrow" and a2 is "a bandit" then do some stuff but if a2 is "a tree" instead, do this instead!

Upvotes: 0

Views: 948

Answers (1)

PoByBolek
PoByBolek

Reputation: 3915

Wouldn't it be better to have some virtual methods in A that do nothing by default and are overwritten by some of its inheriting classes?

class A {
public:
    virtual void method(A *a2) {
    }

    virtual void otherMethod() {
    }
};

class B : public A {
public:
    virtual void method(A *a2) {
        a2->otherMethod();
    }
};

class C : public B {
public:
    virtual void otherMethod() {
        // do your C stuff here
    }
};

class D : public A {
public:
    virtual void otherMethod() {
        // do your D stuff here
    }
};

Would this achieve the things you are trying to do?

Upvotes: 3

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