相关疑难解决方法(0)

我有一个A类:

class A
{
    public:
        virtual double getValue() = 0;
}

和B级:

class B : public A
{
    public:
        virtual double getValue() { return 0.0; }
}

然后在main()中我做:

A * var;
var = new B[100];
std::cout << var[0].getValue(); //This works fine
std::cout << var[1].getValue(); //This, or any other index besides 0, causes the program to quit

如果相反,我做:

B * var;
var = new B[100];
std::cout << var[0].getValue(); //This works fine
std::cout << var[1].getValue(); //Everything else works fine too

一切都很好,但好像我的多态性似乎有些不对劲？我很困惑.

以下代码

#include <iostream>

using namespace std;

class A {};

class B : public A {};

class C : public B {};

void foo(A *a) {
    cout << 'A' << endl;
}

void foo(B *b) {
    cout << 'B' << endl;
}

int main() {
    C *c = new C[10];

    foo(c);
}

编译好并按预期打印'B'.

但是当我改变main()功能时

int main() {
    C c[10];

    foo(c);
}

我收到编译错误说

test_arr.cpp: In function 'int main()':
test_arr.cpp:23:10: error: call of overloaded 'foo(C [10])' is ambiguous
test_arr.cpp:23:10: note: candidates …