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At runtime, the base pointer will be examined. If the conversion is proper, your new Cat pointer will be fine. If the conversion is improper, if you didn't really have a Cat object after all, your new pointer will be null. Listing 18.2 illustrates this. |
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LISTING 18.2 DYNAMIC CAST |
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1: // Listing 18.2 - dynamic cast
2:
3: #include <iostream.h>
4: class Mammal
5: {
6: public:
7: Mammal():itsAge(1) { cout << Mammal constructor\n; }
8: virtual ~Mammal() { cout << Mammal destructor\n; }
9: virtual void Speak() const { cout << Mammal speak!\n; }
10: protected:
11: int itsAge;
12: };
13:
14: class Cat: public Mammal
15: {
16: public:
17: Cat() { cout << Cat constructor\n; }
18: ~Cat() { cout << Cat destructor\n; }
19: void Speak()const { cout << Meow\n; }
20: void Purr() const { cout << rrrrrrrrrrr\n; }
21: };
22:
23: class Dog: public Mammal
24: {
25: public:
26: Dog() { cout << Dog Constructor\n; }
27: ~Dog() { cout << Dog destructor\n; }
28: void Speak()const { cout << Woof!\n; }
29: };
30:
31:
32: int main()
33: {
34: const int NumberMammals = 3;
35: Mammal* Zoo[NumberMammals];
36: Mammal* pMammal;
37: int choice,i;
38: for (i=0; i<NumberMammals; i++)
39: {
40: cout << (1)Dog (2)Cat: ;
41: cin >> choice;
42: if (choice == 1)
43: pMammal = new Dog; |
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continues |
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