72 lines
1.1 KiB
C++
72 lines
1.1 KiB
C++
// 动态类型转换
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#include <iostream>
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using namespace std;
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class A
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{
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protected:
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int x;
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public:
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A(int x) : x(x) {}
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void show()
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{
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cout << "A x = " << x << endl;
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}
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};
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class B : public A
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{
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public:
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B(int x) : A(x) {}
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void print()
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{
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cout << "B print x = " << x << endl;
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}
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};
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class C
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{
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};
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void test1()
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{
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int a = 65;
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// 动态转化不支持基本数据类型之间的转换
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// char c = dynamic_cast<char>(a);
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// char *c = dynamic_cast<char *>(&a);
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// cout << "c = " << c << endl;
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}
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void test2()
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{
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A a1 = A(10);
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B b1 = B(20);
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// 上行转换
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A &a2 = dynamic_cast<A &>(b1);
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a2.show();
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// a2.print(); // 不存在 print 成员函数
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b1.print();
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// 下行转换: 动态转换不支持（安全）
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// B &b2 = dynamic_cast<B &>(a2);
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// b2.print();
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B &b3 = static_cast<B &>(a2);
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b3.print();
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}
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// 不相关类型的转换: 不可动态转换
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void test3()
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{
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A *a = new A(20);
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// C *p = dynamic_cast<C *>(a);
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}
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int main()
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{
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test3();
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return 0;
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}
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