for (int i=0; i < SomeValue; i++)
{
    Class_A *a;
    Class_B *b;

    int SomeID;

    if (SomeFlag != SomeValue)
    {
        a = (Class_A *) some_param;
        SomeID = a->getID;
    }
    else
    {
        b = (Class_B *) some_param;
        SomeID = b->getID;
    }

    switch (SomeID)
    {
        case FIRST_CASE:
            if (SomeFlag != SomeValue)
            {
                SomeArray[i].value = a->FirstMethod;
            }
            else
            {
                SomeArray[i].value = b->FirstMethod;
            }
            break;
        case SECOND_CASE:
            if (SomeFlag != SomeValue)
            {
                SomeArray[i].value = a->SecondMethod;
            }
            else
            {
                SomeArray[i].value = b->SecondMethod;
            }
            break;
    }
}